libavcodec: v4l2: add support for v4l2 mem2mem codecs

    This patchset enhances Alexis Ballier's original patch and validates
    it using Qualcomm's Venus hardware (driver recently landed upstream
    [1]).

    This has been tested on Qualcomm's DragonBoard 410c and 820c
    Configure/make scripts have been validated on Ubuntu 10.04 and
    16.04.

    Tested decoders:
           - h264
           - h263
           - mpeg4
           - vp8
           - vp9
           - hevc

    Tested encoders:
           - h264
           - h263
           - mpeg4

    Tested transcoding (concurrent encoding/decoding)

    Some of the changes introduced:
        - v4l2: code cleanup and abstractions added
        - v4l2: follow the new encode/decode api.
        - v4l2: fix display size for NV12 output pool.
        - v4l2: handle EOS (EPIPE and draining)
        - v4l2: vp8 and mpeg4 decoding and encoding.
        - v4l2: hevc and vp9 support.
        - v4l2: generate EOF on dequeue errors.
        - v4l2: h264_mp4toannexb filtering.
        - v4l2: fixed make install and fate issues.
        - v4l2: codecs enabled/disabled depending on pixfmt defined
        - v4l2: pass timebase/framerate to the context
        - v4l2: runtime decoder reconfiguration.
        - v4l2: add more frame information
        - v4l2: free hardware resources on last reference being released
        - v4l2: encoding: disable b-frames for upstreaming (patch required)

    [1] https://lwn.net/Articles/697956/

    System Level view:
        v42l_m2m_enc/dec --> v4l2_m2m --> v4l2_context --> v4l2_buffers
Reviewed-by: Jorge Ramirez <jorge.ramirez-ortiz@linaro.org>
Reviewed-by: Alexis Ballier <aballier@gentoo.org>
Tested-by: Jorge Ramirez <jorge.ramirez-ortiz@linaro.org>
Signed-off-by: wm4 <nfxjfg@googlemail.com>

Changelog

@@ -49,6 +49,7 @@ version <next>:
 - VP9 tile threading support
 - KMS screen grabber
 - CUDA thumbnail filter
+- V4L2 mem2mem HW assisted codecs
 
 
 version 3.3:

configure

@@ -185,6 +185,7 @@ Individual component options:
   --enable-filter=NAME     enable filter NAME
   --disable-filter=NAME    disable filter NAME
   --disable-filters        disable all filters
+  --disable-v4l2_m2m       disable V4L2 mem2mem code [autodetect]
 
 External library support:
 
@@ -1628,6 +1629,7 @@ HWACCEL_AUTODETECT_LIBRARY_LIST="
     vda
     vdpau
     videotoolbox
+    v4l2_m2m
     xvmc
 "
 
@@ -2755,6 +2757,7 @@ omx_rpi_select="omx"
 qsvdec_select="qsv"
 qsvenc_select="qsv"
 vaapi_encode_deps="vaapi"
+v4l2_m2m_deps_any="linux_videodev2_h"
 
 hwupload_cuda_filter_deps="cuda"
 scale_npp_filter_deps="cuda libnpp"
@@ -2765,6 +2768,8 @@ nvenc_deps="cuda"
 nvenc_deps_any="dlopen LoadLibrary"
 nvenc_encoder_deps="nvenc"
 
+h263_v4l2m2m_decoder_deps="v4l2_m2m h263_v4l2_m2m"
+h263_v4l2m2m_encoder_deps="v4l2_m2m h263_v4l2_m2m"
 h264_crystalhd_decoder_select="crystalhd h264_mp4toannexb_bsf h264_parser"
 h264_cuvid_decoder_deps="cuda cuvid"
 h264_cuvid_decoder_select="h264_mp4toannexb_bsf"
@@ -2783,6 +2788,8 @@ h264_vda_decoder_deps="vda"
 h264_vda_decoder_select="h264_decoder"
 h264_vdpau_decoder_deps="vdpau"
 h264_vdpau_decoder_select="h264_decoder"
+h264_v4l2m2m_decoder_deps="v4l2_m2m h264_v4l2_m2m"
+h264_v4l2m2m_encoder_deps="v4l2_m2m h264_v4l2_m2m"
 hevc_cuvid_decoder_deps="cuda cuvid"
 hevc_cuvid_decoder_select="hevc_mp4toannexb_bsf"
 hevc_mediacodec_decoder_deps="mediacodec"
@@ -2794,12 +2801,15 @@ hevc_qsv_encoder_deps="libmfx"
 hevc_qsv_encoder_select="hevcparse qsvenc"
 hevc_vaapi_encoder_deps="VAEncPictureParameterBufferHEVC"
 hevc_vaapi_encoder_select="vaapi_encode golomb"
+hevc_v4l2m2m_decoder_deps="v4l2_m2m hevc_v4l2_m2m"
+hevc_v4l2m2m_encoder_deps="v4l2_m2m hevc_v4l2_m2m"
 mjpeg_cuvid_decoder_deps="cuda cuvid"
 mjpeg_vaapi_encoder_deps="VAEncPictureParameterBufferJPEG"
 mjpeg_vaapi_encoder_select="vaapi_encode jpegtables"
 mpeg1_cuvid_decoder_deps="cuda cuvid"
 mpeg1_vdpau_decoder_deps="vdpau"
 mpeg1_vdpau_decoder_select="mpeg1video_decoder"
+mpeg1_v4l2m2m_decoder_deps="v4l2_m2m mpeg1_v4l2_m2m"
 mpeg2_crystalhd_decoder_select="crystalhd"
 mpeg2_cuvid_decoder_deps="cuda cuvid"
 mpeg2_mmal_decoder_deps="mmal"
@@ -2810,6 +2820,7 @@ mpeg2_qsv_encoder_deps="libmfx"
 mpeg2_qsv_encoder_select="qsvenc"
 mpeg2_vaapi_encoder_deps="VAEncPictureParameterBufferMPEG2"
 mpeg2_vaapi_encoder_select="vaapi_encode"
+mpeg2_v4l2m2m_decoder_deps="v4l2_m2m mpeg2_v4l2_m2m"
 mpeg4_crystalhd_decoder_select="crystalhd"
 mpeg4_cuvid_decoder_deps="cuda cuvid"
 mpeg4_mediacodec_decoder_deps="mediacodec"
@@ -2817,6 +2828,8 @@ mpeg4_mmal_decoder_deps="mmal"
 mpeg4_omx_encoder_deps="omx"
 mpeg4_vdpau_decoder_deps="vdpau"
 mpeg4_vdpau_decoder_select="mpeg4_decoder"
+mpeg4_v4l2m2m_decoder_deps="v4l2_m2m mpeg4_v4l2_m2m"
+mpeg4_v4l2m2m_encoder_deps="v4l2_m2m mpeg4_v4l2_m2m"
 mpeg_vdpau_decoder_deps="vdpau"
 mpeg_vdpau_decoder_select="mpeg2video_decoder"
 msmpeg4_crystalhd_decoder_select="crystalhd"
@@ -2827,16 +2840,20 @@ vc1_cuvid_decoder_deps="cuda cuvid"
 vc1_mmal_decoder_deps="mmal"
 vc1_vdpau_decoder_deps="vdpau"
 vc1_vdpau_decoder_select="vc1_decoder"
+vc1_v4l2m2m_decoder_deps="v4l2_m2m vc1_v4l2_m2m"
 vp8_cuvid_decoder_deps="cuda cuvid"
 vp8_mediacodec_decoder_deps="mediacodec"
 vp8_qsv_decoder_deps="libmfx"
 vp8_qsv_decoder_select="qsvdec vp8_qsv_hwaccel vp8_parser"
 vp8_vaapi_encoder_deps="VAEncPictureParameterBufferVP8"
 vp8_vaapi_encoder_select="vaapi_encode"
+vp8_v4l2m2m_decoder_deps="v4l2_m2m vp8_v4l2_m2m"
+vp8_v4l2m2m_encoder_deps="v4l2_m2m vp8_v4l2_m2m"
 vp9_cuvid_decoder_deps="cuda cuvid"
 vp9_mediacodec_decoder_deps="mediacodec"
 vp9_vaapi_encoder_deps="VAEncPictureParameterBufferVP9"
 vp9_vaapi_encoder_select="vaapi_encode"
+vp9_v4l2m2m_decoder_deps="v4l2_m2m vp9_v4l2_m2m"
 wmv3_crystalhd_decoder_select="crystalhd"
 wmv3_vdpau_decoder_select="vc1_vdpau_decoder"
 
@@ -6109,9 +6126,20 @@ perl -v            > /dev/null 2>&1 && enable perl      || disable perl
 pod2man --help     > /dev/null 2>&1 && enable pod2man   || disable pod2man
 rsync --help 2> /dev/null | grep -q 'contimeout' && enable rsync_contimeout || disable rsync_contimeout
 
+# check V4L2 codecs available in the API
 check_header linux/fb.h
 check_header linux/videodev2.h
 check_code cc linux/videodev2.h "struct v4l2_frmsizeenum vfse; vfse.discrete.width = 0;" && enable_safe struct_v4l2_frmivalenum_discrete
+check_code cc linux/videodev2.h "int i = V4L2_CAP_VIDEO_M2M_MPLANE | V4L2_CAP_VIDEO_M2M | V4L2_BUF_FLAG_LAST;" || disable v4l2_m2m
+check_code cc linux/videodev2.h "int i = V4L2_PIX_FMT_VC1_ANNEX_G;" && enable vc1_v4l2_m2m
+check_code cc linux/videodev2.h "int i = V4L2_PIX_FMT_MPEG1;" && enable mpeg1_v4l2_m2m
+check_code cc linux/videodev2.h "int i = V4L2_PIX_FMT_MPEG2;" && enable mpeg2_v4l2_m2m
+check_code cc linux/videodev2.h "int i = V4L2_PIX_FMT_MPEG4;" && enable mpeg4_v4l2_m2m
+check_code cc linux/videodev2.h "int i = V4L2_PIX_FMT_HEVC;" && enable hevc_v4l2_m2m
+check_code cc linux/videodev2.h "int i = V4L2_PIX_FMT_H263;" && enable h263_v4l2_m2m
+check_code cc linux/videodev2.h "int i = V4L2_PIX_FMT_H264;" && enable h264_v4l2_m2m
+check_code cc linux/videodev2.h "int i = V4L2_PIX_FMT_VP8;" && enable vp8_v4l2_m2m
+check_code cc linux/videodev2.h "int i = V4L2_PIX_FMT_VP9;" && enable vp9_v4l2_m2m
 
 check_header sys/videoio.h
 check_code cc sys/videoio.h "struct v4l2_frmsizeenum vfse; vfse.discrete.width = 0;" && enable_safe struct_v4l2_frmivalenum_discrete

libavcodec/Makefile

@@ -137,6 +137,7 @@ OBJS-$(CONFIG_VIDEODSP)                += videodsp.o
 OBJS-$(CONFIG_VP3DSP)                  += vp3dsp.o
 OBJS-$(CONFIG_VP56DSP)                 += vp56dsp.o
 OBJS-$(CONFIG_VP8DSP)                  += vp8dsp.o
+OBJS-$(CONFIG_V4L2_M2M)                += v4l2_m2m.o v4l2_context.o v4l2_buffers.o v4l2_fmt.o
 OBJS-$(CONFIG_WMA_FREQS)               += wma_freqs.o
 OBJS-$(CONFIG_WMV2DSP)                 += wmv2dsp.o
 
@@ -323,6 +324,8 @@ OBJS-$(CONFIG_H263_DECODER)            += h263dec.o h263.o ituh263dec.o        \
                                           intelh263dec.o h263data.o
 OBJS-$(CONFIG_H263_ENCODER)            += mpeg4videoenc.o mpeg4video.o  \
                                           h263.o ituh263enc.o flvenc.o h263data.o
+OBJS-$(CONFIG_H263_V4L2M2M_DECODER)    += v4l2_m2m_dec.o
+OBJS-$(CONFIG_H263_V4L2M2M_ENCODER)    += v4l2_m2m_enc.o
 OBJS-$(CONFIG_H264_DECODER)            += h264dec.o h264_cabac.o h264_cavlc.o \
                                           h264_direct.o h264_loopfilter.o  \
                                           h264_mb.o h264_picture.o \
@@ -340,6 +343,8 @@ OBJS-$(CONFIG_H264_QSV_DECODER)        += qsvdec_h2645.o
 OBJS-$(CONFIG_H264_QSV_ENCODER)        += qsvenc_h264.o
 OBJS-$(CONFIG_H264_VAAPI_ENCODER)      += vaapi_encode_h264.o vaapi_encode_h26x.o
 OBJS-$(CONFIG_H264_VIDEOTOOLBOX_ENCODER) += videotoolboxenc.o
+OBJS-$(CONFIG_H264_V4L2M2M_DECODER)    += v4l2_m2m_dec.o
+OBJS-$(CONFIG_H264_V4L2M2M_ENCODER)    += v4l2_m2m_enc.o
 OBJS-$(CONFIG_HAP_DECODER)             += hapdec.o hap.o
 OBJS-$(CONFIG_HAP_ENCODER)             += hapenc.o hap.o
 OBJS-$(CONFIG_HEVC_DECODER)            += hevcdec.o hevc_mvs.o \
@@ -353,6 +358,8 @@ OBJS-$(CONFIG_HEVC_QSV_DECODER)        += qsvdec_h2645.o
 OBJS-$(CONFIG_HEVC_QSV_ENCODER)        += qsvenc_hevc.o hevc_ps_enc.o       \
                                           hevc_data.o
 OBJS-$(CONFIG_HEVC_VAAPI_ENCODER)      += vaapi_encode_h265.o vaapi_encode_h26x.o
+OBJS-$(CONFIG_HEVC_V4L2M2M_DECODER)    += v4l2_m2m_dec.o
+OBJS-$(CONFIG_HEVC_V4L2M2M_ENCODER)    += v4l2_m2m_enc.o
 OBJS-$(CONFIG_HNM4_VIDEO_DECODER)      += hnm4video.o
 OBJS-$(CONFIG_HQ_HQA_DECODER)          += hq_hqa.o hq_hqadata.o hq_hqadsp.o \
                                           canopus.o
@@ -422,6 +429,7 @@ OBJS-$(CONFIG_MPC8_DECODER)            += mpc8.o mpc.o
 OBJS-$(CONFIG_MPEGVIDEO_DECODER)       += mpeg12dec.o mpeg12.o mpeg12data.o
 OBJS-$(CONFIG_MPEG1VIDEO_DECODER)      += mpeg12dec.o mpeg12.o mpeg12data.o
 OBJS-$(CONFIG_MPEG1VIDEO_ENCODER)      += mpeg12enc.o mpeg12.o
+OBJS-$(CONFIG_MPEG1_V4L2M2M_DECODER)   += v4l2_m2m_dec.o
 OBJS-$(CONFIG_MPEG2_MMAL_DECODER)      += mmaldec.o
 OBJS-$(CONFIG_MPEG2_QSV_DECODER)       += qsvdec_other.o
 OBJS-$(CONFIG_MPEG2_QSV_ENCODER)       += qsvenc_mpeg2.o
@@ -429,9 +437,12 @@ OBJS-$(CONFIG_MPEG2VIDEO_DECODER)      += mpeg12dec.o mpeg12.o mpeg12data.o
 OBJS-$(CONFIG_MPEG2VIDEO_ENCODER)      += mpeg12enc.o mpeg12.o
 OBJS-$(CONFIG_MPEG2_MEDIACODEC_DECODER) += mediacodecdec.o
 OBJS-$(CONFIG_MPEG2_VAAPI_ENCODER)     += vaapi_encode_mpeg2.o
+OBJS-$(CONFIG_MPEG2_V4L2M2M_DECODER)   += v4l2_m2m_dec.o
 OBJS-$(CONFIG_MPEG4_DECODER)           += xvididct.o
 OBJS-$(CONFIG_MPEG4_MEDIACODEC_DECODER) += mediacodecdec.o
 OBJS-$(CONFIG_MPEG4_OMX_ENCODER)       += omx.o
+OBJS-$(CONFIG_MPEG4_V4L2M2M_DECODER)   += v4l2_m2m_dec.o
+OBJS-$(CONFIG_MPEG4_V4L2M2M_ENCODER)   += v4l2_m2m_enc.o
 OBJS-$(CONFIG_MPL2_DECODER)            += mpl2dec.o ass.o
 OBJS-$(CONFIG_MSA1_DECODER)            += mss3.o
 OBJS-$(CONFIG_MSCC_DECODER)            += mscc.o
@@ -605,6 +616,7 @@ OBJS-$(CONFIG_VC1_DECODER)             += vc1dec.o vc1_block.o vc1_loopfilter.o
 OBJS-$(CONFIG_VC1_CUVID_DECODER)       += cuvid.o
 OBJS-$(CONFIG_VC1_MMAL_DECODER)        += mmaldec.o
 OBJS-$(CONFIG_VC1_QSV_DECODER)         += qsvdec_other.o
+OBJS-$(CONFIG_VC1_V4L2M2M_DECODER)     += v4l2_m2m_dec.o
 OBJS-$(CONFIG_VC2_ENCODER)             += vc2enc.o vc2enc_dwt.o diractab.o
 OBJS-$(CONFIG_VCR1_DECODER)            += vcr1.o
 OBJS-$(CONFIG_VMDAUDIO_DECODER)        += vmdaudio.o
@@ -624,6 +636,8 @@ OBJS-$(CONFIG_VP8_CUVID_DECODER)       += cuvid.o
 OBJS-$(CONFIG_VP8_MEDIACODEC_DECODER)  += mediacodecdec.o
 OBJS-$(CONFIG_VP8_QSV_DECODER)         += qsvdec_other.o
 OBJS-$(CONFIG_VP8_VAAPI_ENCODER)       += vaapi_encode_vp8.o
+OBJS-$(CONFIG_VP8_V4L2M2M_DECODER)     += v4l2_m2m_dec.o
+OBJS-$(CONFIG_VP8_V4L2M2M_ENCODER)     += v4l2_m2m_enc.o
 OBJS-$(CONFIG_VP9_DECODER)             += vp9.o vp9data.o vp9dsp.o vp9lpf.o vp9recon.o \
                                           vp9block.o vp9prob.o vp9mvs.o vp56rac.o \
                                           vp9dsp_8bpp.o vp9dsp_10bpp.o vp9dsp_12bpp.o
@@ -631,6 +645,7 @@ OBJS-$(CONFIG_VP9_CUVID_DECODER)       += cuvid.o
 OBJS-$(CONFIG_VP9_MEDIACODEC_DECODER)  += mediacodecdec.o
 OBJS-$(CONFIG_VP9_VAAPI_ENCODER)       += vaapi_encode_vp9.o
 OBJS-$(CONFIG_VPLAYER_DECODER)         += textdec.o ass.o
+OBJS-$(CONFIG_VP9_V4L2M2M_DECODER)     += v4l2_m2m_dec.o
 OBJS-$(CONFIG_VQA_DECODER)             += vqavideo.o
 OBJS-$(CONFIG_WAVPACK_DECODER)         += wavpack.o
 OBJS-$(CONFIG_WAVPACK_ENCODER)         += wavpackenc.o

libavcodec/allcodecs.c

@@ -208,8 +208,10 @@ static void register_all(void)
     REGISTER_ENCDEC (H263,              h263);
     REGISTER_DECODER(H263I,             h263i);
     REGISTER_ENCDEC (H263P,             h263p);
+    REGISTER_ENCDEC (H263_V4L2M2M,      h263_v4l2m2m);
     REGISTER_DECODER(H264,              h264);
     REGISTER_DECODER(H264_CRYSTALHD,    h264_crystalhd);
+    REGISTER_ENCDEC (H264_V4L2M2M,      h264_v4l2m2m);
     REGISTER_DECODER(H264_MEDIACODEC,   h264_mediacodec);
     REGISTER_DECODER(H264_MMAL,         h264_mmal);
     REGISTER_DECODER(H264_QSV,          h264_qsv);
@@ -220,6 +222,7 @@ static void register_all(void)
     REGISTER_ENCDEC (HAP,               hap);
     REGISTER_DECODER(HEVC,              hevc);
     REGISTER_DECODER(HEVC_QSV,          hevc_qsv);
+    REGISTER_ENCDEC (HEVC_V4L2M2M,      hevc_v4l2m2m);
     REGISTER_DECODER(HNM4_VIDEO,        hnm4_video);
     REGISTER_DECODER(HQ_HQA,            hq_hqa);
     REGISTER_DECODER(HQX,               hqx);
@@ -254,6 +257,7 @@ static void register_all(void)
     REGISTER_ENCDEC (MPEG2VIDEO,        mpeg2video);
     REGISTER_ENCDEC (MPEG4,             mpeg4);
     REGISTER_DECODER(MPEG4_CRYSTALHD,   mpeg4_crystalhd);
+    REGISTER_ENCDEC (MPEG4_V4L2M2M,     mpeg4_v4l2m2m);
     REGISTER_DECODER(MPEG4_MMAL,        mpeg4_mmal);
 #if FF_API_VDPAU
     REGISTER_DECODER(MPEG4_VDPAU,       mpeg4_vdpau);
@@ -263,8 +267,10 @@ static void register_all(void)
     REGISTER_DECODER(MPEG_VDPAU,        mpeg_vdpau);
     REGISTER_DECODER(MPEG1_VDPAU,       mpeg1_vdpau);
 #endif
+    REGISTER_DECODER(MPEG1_V4L2M2M,     mpeg1_v4l2m2m);
     REGISTER_DECODER(MPEG2_MMAL,        mpeg2_mmal);
     REGISTER_DECODER(MPEG2_CRYSTALHD,   mpeg2_crystalhd);
+    REGISTER_DECODER(MPEG2_V4L2M2M,     mpeg2_v4l2m2m);
     REGISTER_DECODER(MPEG2_QSV,         mpeg2_qsv);
     REGISTER_DECODER(MPEG2_MEDIACODEC,  mpeg2_mediacodec);
     REGISTER_DECODER(MSA1,              msa1);
@@ -362,6 +368,7 @@ static void register_all(void)
     REGISTER_DECODER(VC1IMAGE,          vc1image);
     REGISTER_DECODER(VC1_MMAL,          vc1_mmal);
     REGISTER_DECODER(VC1_QSV,           vc1_qsv);
+    REGISTER_DECODER(VC1_V4L2M2M,       vc1_v4l2m2m);
     REGISTER_ENCODER(VC2,               vc2);
     REGISTER_DECODER(VCR1,              vcr1);
     REGISTER_DECODER(VMDVIDEO,          vmdvideo);
@@ -373,7 +380,9 @@ static void register_all(void)
     REGISTER_DECODER(VP6F,              vp6f);
     REGISTER_DECODER(VP7,               vp7);
     REGISTER_DECODER(VP8,               vp8);
+    REGISTER_ENCDEC (VP8_V4L2M2M,       vp8_v4l2m2m);
     REGISTER_DECODER(VP9,               vp9);
+    REGISTER_DECODER(VP9_V4L2M2M,       vp9_v4l2m2m);
     REGISTER_DECODER(VQA,               vqa);
     REGISTER_DECODER(BITPACKED,         bitpacked);
     REGISTER_DECODER(WEBP,              webp);

libavcodec/v4l2_buffers.h

+/*
+ * V4L2 buffer helper functions.
+ *
+ * Copyright (C) 2017 Alexis Ballier <aballier@gentoo.org>
+ * Copyright (C) 2017 Jorge Ramirez <jorge.ramirez-ortiz@linaro.org>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef AVCODEC_V4L2_BUFFERS_H
+#define AVCODEC_V4L2_BUFFERS_H
+
+enum V4L2Buffer_status {
+    V4L2BUF_AVAILABLE,
+    V4L2BUF_IN_DRIVER,
+    V4L2BUF_RET_USER,
+};
+
+/**
+ * V4L2Buffer (wrapper for v4l2_buffer management)
+ */
+typedef struct V4L2Buffer {
+    /* each buffer needs to have a reference to its context */
+    struct V4L2Context *context;
+
+    /* keep track of the mmap address and mmap length */
+    struct V4L2Plane_info {
+        int bytesperline;
+        void * mm_addr;
+        size_t length;
+    } plane_info[VIDEO_MAX_PLANES];
+
+    int num_planes;
+
+    /* the v4l2_buffer buf.m.planes pointer uses the planes[] mem */
+    struct v4l2_buffer buf;
+    struct v4l2_plane planes[VIDEO_MAX_PLANES];
+
+    int flags;
+    enum V4L2Buffer_status status;
+
+} V4L2Buffer;
+
+/**
+ * Extracts the data from a V4L2Buffer to an AVFrame
+ *
+ * @param[in] frame The AVFRame to push the information to
+ * @param[in] buf The V4L2Buffer to get the information from
+ *
+ * @returns 0 in case of success, EINVAL if the number of planes is incorrect,
+ * ENOMEM if the AVBufferRef cant be created.
+ */
+int ff_v4l2_buffer_buf_to_avframe(AVFrame *frame, V4L2Buffer *buf);
+
+/**
+ * Extracts the data from a V4L2Buffer to an AVPacket
+ *
+ * @param[in] pkt The AVPacket to push the information to
+ * @param[in] buf The V4L2Buffer to get the information from
+ *
+ * @returns 0 in case of success, EINVAL if the number of planes is incorrect,
+ * ENOMEM if the AVBufferRef cant be created.
+ *
+ */
+int ff_v4l2_buffer_buf_to_avpkt(AVPacket *pkt, V4L2Buffer *buf);
+
+/**
+ * Extracts the data from an AVPacket to a V4L2Buffer
+ *
+ * @param[in]  frame AVPacket to get the data from
+ * @param[in]  avbuf V4L2Bfuffer to push the information to
+ *
+ * @returns 0 in case of success, negative otherwise
+ */
+int ff_v4l2_buffer_avpkt_to_buf(const AVPacket *pkt, V4L2Buffer *out);
+
+/**
+ * Extracts the data from an AVFrame to a V4L2Buffer
+ *
+ * @param[in]  frame AVFrame to get the data from
+ * @param[in]  avbuf V4L2Bfuffer to push the information to
+ *
+ * @returns 0 in case of success, negative otherwise
+ */
+int ff_v4l2_buffer_avframe_to_buf(const AVFrame *frame, V4L2Buffer* out);
+
+/**
+ * Initializes a V4L2Buffer
+ *
+ * @param[in]  avbuf V4L2Bfuffer to initialize
+ * @param[in]  index v4l2 buffer id
+ *
+ * @returns 0 in case of success, negative otherwise
+ */
+int ff_v4l2_buffer_initialize(V4L2Buffer* avbuf, int index);
+
+/**
+ * Enqueues a V4L2Buffer
+ *
+ * @param[in] avbuf V4L2Bfuffer to push to the driver
+ *
+ * @returns 0 in case of success, negative otherwise
+ */
+int ff_v4l2_buffer_enqueue(V4L2Buffer* avbuf);
+
+
+#endif // AVCODEC_V4L2_BUFFERS_H

libavcodec/v4l2_context.h

+/*
+ * V4L2 context helper functions.
+ *
+ * Copyright (C) 2017 Alexis Ballier <aballier@gentoo.org>
+ * Copyright (C) 2017 Jorge Ramirez <jorge.ramirez-ortiz@linaro.org>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef AVCODEC_V4L2_CONTEXT_H
+#define AVCODEC_V4L2_CONTEXT_H
+
+#include <stdatomic.h>
+#include "libavcodec/avcodec.h"
+#include "libavutil/pixfmt.h"
+#include "libavutil/frame.h"
+#include "libavutil/buffer.h"
+#include "v4l2_buffers.h"
+
+typedef struct V4L2Context {
+    /**
+     * context name.
+     */
+    const char* name;
+
+    /**
+     * Type of this buffer context.
+     * See V4L2_BUF_TYPE_VIDEO_* in videodev2.h
+     * Readonly after init.
+     */
+    enum v4l2_buf_type type;
+
+    /**
+     * AVPixelFormat corresponding to this buffer context.
+     * AV_PIX_FMT_NONE means this is an encoded stream.
+     */
+    enum AVPixelFormat av_pix_fmt;
+
+    /**
+     * AVCodecID corresponding to this buffer context.
+     * AV_CODEC_ID_RAWVIDEO means this is a raw stream and av_pix_fmt must be set to a valid value.
+     */
+    enum AVCodecID av_codec_id;
+
+    /**
+     * Format returned by the driver after initializing the buffer context.
+     * Readonly after init.
+     */
+    struct v4l2_format format;
+
+    /**
+     * Width and height of the frames it produces (in case of a capture context, e.g. when decoding)
+     * or accepts (in case of an output context, e.g. when encoding).
+     */
+    int width, height;
+
+    /**
+     * Indexed array of V4L2Buffers
+     */
+    V4L2Buffer *buffers;
+
+    /**
+     * Readonly after init.
+     */
+    int num_buffers;
+
+    /**
+     * Whether the stream has been started (VIDIOC_STREAMON has been sent).
+     */
+    int streamon;
+
+    /**
+     *  Either no more buffers available or an unrecoverable error was notified
+     *  by the V4L2 kernel driver: once set the context has to be exited.
+     */
+    int done;
+
+} V4L2Context;
+
+/**
+ * Initializes a V4L2Context.
+ *
+ * @param[in] ctx A pointer to a V4L2Context. See V4L2Context description for required variables.
+ * @return 0 in case of success, a negative value representing the error otherwise.
+ */
+int ff_v4l2_context_init(V4L2Context* ctx);
+
+/**
+ * Sets the V4L2Context format in the v4l2 driver.
+ *
+ * @param[in] ctx A pointer to a V4L2Context. See V4L2Context description for required variables.
+ * @return 0 in case of success, a negative value representing the error otherwise.
+ */
+int ff_v4l2_context_set_format(V4L2Context* ctx);
+
+/**
+ * Queries the driver for a valid v4l2 format and copies it to the context.
+ *
+ * @param[in] ctx A pointer to a V4L2Context. See V4L2Context description for required variables.
+ * @return 0 in case of success, a negative value representing the error otherwise.
+ */
+int ff_v4l2_context_get_format(V4L2Context* ctx);
+
+/**
+ * Releases a V4L2Context.
+ *
+ * @param[in] ctx A pointer to a V4L2Context.
+ *               The caller is reponsible for freeing it.
+ *               It must not be used after calling this function.
+ */
+void ff_v4l2_context_release(V4L2Context* ctx);
+
+/**
+ * Sets the status of a V4L2Context.
+ *
+ * @param[in] ctx A pointer to a V4L2Context.
+ * @param[in] cmd The status to set (VIDIOC_STREAMON or VIDIOC_STREAMOFF).
+ *                Warning: If VIDIOC_STREAMOFF is sent to a buffer context that still has some frames buffered,
+ *                those frames will be dropped.
+ * @return 0 in case of success, a negative value representing the error otherwise.
+ */
+int ff_v4l2_context_set_status(V4L2Context* ctx, int cmd);
+
+/**
+ * Dequeues a buffer from a V4L2Context to an AVPacket.
+ *
+ * The pkt must be non NULL.
+ * @param[in] ctx The V4L2Context to dequeue from.
+ * @param[inout] pkt The AVPacket to dequeue to.
+ * @return 0 in case of success, AVERROR(EAGAIN) if no buffer was ready, another negative error in case of error.
+ */
+int ff_v4l2_context_dequeue_packet(V4L2Context* ctx, AVPacket* pkt);
+
+/**
+ * Dequeues a buffer from a V4L2Context to an AVFrame.
+ *
+ * The frame must be non NULL.
+ * @param[in] ctx The V4L2Context to dequeue from.
+ * @param[inout] f The AVFrame to dequeue to.
+ * @return 0 in case of success, AVERROR(EAGAIN) if no buffer was ready, another negative error in case of error.
+ */
+int ff_v4l2_context_dequeue_frame(V4L2Context* ctx, AVFrame* f);
+
+/**
+ * Enqueues a buffer to a V4L2Context from an AVPacket
+ *
+ * The packet must be non NULL.
+ * When the size of the pkt is null, the buffer is not queued but a V4L2_DEC_CMD_STOP command is sent instead to the driver.
+ *
+ * @param[in] ctx The V4L2Context to enqueue to.
+ * @param[in] pkt A pointer to an AVPacket.
+ * @return 0 in case of success, a negative error otherwise.
+ */
+int ff_v4l2_context_enqueue_packet(V4L2Context* ctx, const AVPacket* pkt);
+
+/**
+ * Enqueues a buffer to a V4L2Context from an AVFrame
+ *
+ * The frame must be non NULL.
+ *
+ * @param[in] ctx The V4L2Context to enqueue to.
+ * @param[in] f A pointer to an AVFrame to enqueue.
+ * @return 0 in case of success, a negative error otherwise.
+ */
+int ff_v4l2_context_enqueue_frame(V4L2Context* ctx, const AVFrame* f);
+
+#endif // AVCODEC_V4L2_CONTEXT_H

libavcodec/v4l2_fmt.c

+/*
+ * V4L2 format helper functions
+ *
+ * Copyright (C) 2017 Alexis Ballier <aballier@gentoo.org>
+ * Copyright (C) 2017 Jorge Ramirez <jorge.ramirez-ortiz@linaro.org>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <linux/videodev2.h>
+#include <search.h>
+#include "v4l2_fmt.h"
+
+#define V4L2_FMT(x) V4L2_PIX_FMT_##x
+#define AV_CODEC(x) AV_CODEC_ID_##x
+#define AV_FMT(x)   AV_PIX_FMT_##x
+
+static const struct fmt_conversion {
+    enum AVPixelFormat avfmt;
+    enum AVCodecID avcodec;
+    uint32_t v4l2_fmt;
+} fmt_map[] = {
+    { AV_FMT(RGB555LE),    AV_CODEC(RAWVIDEO),    V4L2_FMT(RGB555) },
+    { AV_FMT(RGB555BE),    AV_CODEC(RAWVIDEO),    V4L2_FMT(RGB555X) },
+    { AV_FMT(RGB565LE),    AV_CODEC(RAWVIDEO),    V4L2_FMT(RGB565) },
+    { AV_FMT(RGB565BE),    AV_CODEC(RAWVIDEO),    V4L2_FMT(RGB565X) },
+    { AV_FMT(BGR24),       AV_CODEC(RAWVIDEO),    V4L2_FMT(BGR24) },
+    { AV_FMT(RGB24),       AV_CODEC(RAWVIDEO),    V4L2_FMT(RGB24) },
+    { AV_FMT(BGR0),        AV_CODEC(RAWVIDEO),    V4L2_FMT(BGR32) },
+    { AV_FMT(0RGB),        AV_CODEC(RAWVIDEO),    V4L2_FMT(RGB32) },
+    { AV_FMT(GRAY8),       AV_CODEC(RAWVIDEO),    V4L2_FMT(GREY) },
+    { AV_FMT(YUV420P),     AV_CODEC(RAWVIDEO),    V4L2_FMT(YUV420) },
+    { AV_FMT(YUYV422),     AV_CODEC(RAWVIDEO),    V4L2_FMT(YUYV) },
+    { AV_FMT(UYVY422),     AV_CODEC(RAWVIDEO),    V4L2_FMT(UYVY) },
+    { AV_FMT(YUV422P),     AV_CODEC(RAWVIDEO),    V4L2_FMT(YUV422P) },
+    { AV_FMT(YUV411P),     AV_CODEC(RAWVIDEO),    V4L2_FMT(YUV411P) },
+    { AV_FMT(YUV410P),     AV_CODEC(RAWVIDEO),    V4L2_FMT(YUV410) },
+    { AV_FMT(YUV410P),     AV_CODEC(RAWVIDEO),    V4L2_FMT(YVU410) },
+    { AV_FMT(NV12),        AV_CODEC(RAWVIDEO),    V4L2_FMT(NV12) },
+    { AV_FMT(NONE),        AV_CODEC(MJPEG),       V4L2_FMT(MJPEG) },
+    { AV_FMT(NONE),        AV_CODEC(MJPEG),       V4L2_FMT(JPEG) },
+#ifdef V4L2_PIX_FMT_SRGGB8
+    { AV_FMT(BAYER_BGGR8), AV_CODEC(RAWVIDEO),    V4L2_FMT(SBGGR8) },
+    { AV_FMT(BAYER_GBRG8), AV_CODEC(RAWVIDEO),    V4L2_FMT(SGBRG8) },
+    { AV_FMT(BAYER_GRBG8), AV_CODEC(RAWVIDEO),    V4L2_FMT(SGRBG8) },
+    { AV_FMT(BAYER_RGGB8), AV_CODEC(RAWVIDEO),    V4L2_FMT(SRGGB8) },
+#endif
+#ifdef V4L2_PIX_FMT_Y16
+    { AV_FMT(GRAY16LE),    AV_CODEC(RAWVIDEO),    V4L2_FMT(Y16) },
+#endif
+#ifdef V4L2_PIX_FMT_NV12M
+    { AV_FMT(NV12),        AV_CODEC(RAWVIDEO),    V4L2_FMT(NV12M) },
+#endif
+#ifdef V4L2_PIX_FMT_NV21M
+    { AV_FMT(NV21),        AV_CODEC(RAWVIDEO),    V4L2_FMT(NV21M) },
+#endif
+#ifdef V4L2_PIX_FMT_YUV420M
+    { AV_FMT(YUV420P),     AV_CODEC(RAWVIDEO),    V4L2_FMT(YUV420M) },
+#endif
+#ifdef V4L2_PIX_FMT_NV16M
+    { AV_FMT(NV16),        AV_CODEC(RAWVIDEO),    V4L2_FMT(NV16M) },
+#endif
+#ifdef V4L2_PIX_FMT_H263
+    { AV_FMT(NONE),        AV_CODEC(H263),        V4L2_FMT(H263) },
+#endif
+#ifdef V4L2_PIX_FMT_H264
+    { AV_FMT(NONE),        AV_CODEC(H264),        V4L2_FMT(H264) },
+#endif
+#ifdef V4L2_PIX_FMT_MPEG4
+    { AV_FMT(NONE),        AV_CODEC(MPEG4),       V4L2_FMT(MPEG4) },
+#endif
+#ifdef V4L2_PIX_FMT_CPIA1
+    { AV_FMT(NONE),        AV_CODEC(CPIA),        V4L2_FMT(CPIA1) },
+#endif
+#ifdef V4L2_PIX_FMT_DV
+    { AV_FMT(NONE),        AV_CODEC(DVVIDEO),     V4L2_FMT(DV) },
+#endif
+#ifdef V4L2_PIX_FMT_MPEG1
+    { AV_FMT(NONE),        AV_CODEC(MPEG1VIDEO),  V4L2_FMT(MPEG1) },
+#endif
+#ifdef V4L2_PIX_FMT_MPEG2
+    { AV_FMT(NONE),        AV_CODEC(MPEG2VIDEO),  V4L2_FMT(MPEG2) },
+#endif
+#ifdef V4L2_PIX_FMT_VP8
+    { AV_FMT(NONE),        AV_CODEC(VP8),         V4L2_FMT(VP8) },
+#endif
+#ifdef V4L2_PIX_FMT_VP9
+    { AV_FMT(NONE),        AV_CODEC(VP9),         V4L2_FMT(VP9) },
+#endif
+#ifdef V4L2_PIX_FMT_HEVC
+    { AV_FMT(NONE),        AV_CODEC(HEVC),        V4L2_FMT(HEVC) },
+#endif
+#ifdef V4L2_PIX_FMT_VC1_ANNEX_G
+    { AV_FMT(NONE),        AV_CODEC(VC1),         V4L2_FMT(VC1_ANNEX_G) },
+#endif
+};
+
+static int match_codec(const void *a, const void *b)
+{
+    if (*(enum AVCodecID *)a == ((struct fmt_conversion *)b)->avcodec)
+        return 0;
+
+    return 1;
+}
+
+uint32_t ff_v4l2_format_avcodec_to_v4l2(enum AVCodecID avcodec)
+{
+    size_t len = FF_ARRAY_ELEMS(fmt_map);
+    struct fmt_conversion *item;
+
+    item = lfind(&avcodec, fmt_map, &len, sizeof(fmt_map[0]), match_codec);
+    if (item)
+        return item->v4l2_fmt;
+
+    return 0;
+}
+
+static int match_fmt(const void *a, const void *b)
+{
+    if ( *(enum AVPixelFormat *)a == ((struct fmt_conversion *)b)->avfmt)
+        return 0;
+
+    return 1;
+}
+
+uint32_t ff_v4l2_format_avfmt_to_v4l2(enum AVPixelFormat avfmt)
+{
+    size_t len = FF_ARRAY_ELEMS(fmt_map);
+    struct fmt_conversion *item;
+
+    item = lfind(&avfmt, fmt_map, &len, sizeof(fmt_map[0]), match_fmt);
+    if (item)
+        return item->v4l2_fmt;
+
+    return 0;
+}
+
+struct v4l2fmt_avcodec_pair {
+    enum AVCodecID avcodec;
+    uint32_t v4l2_fmt;
+};
+
+static int match_codecfmt(const void *a, const void *b)
+{
+    struct v4l2fmt_avcodec_pair *key = (struct v4l2fmt_avcodec_pair *) a;
+    struct fmt_conversion *item = (struct fmt_conversion *) b;
+
+    if (key->avcodec == item->avcodec && key->v4l2_fmt == item->v4l2_fmt)
+        return 0;
+
+    return 1;
+}
+
+enum AVPixelFormat ff_v4l2_format_v4l2_to_avfmt(uint32_t v4l2_fmt, enum AVCodecID avcodec)
+{
+    struct v4l2fmt_avcodec_pair const key = {
+        .v4l2_fmt = v4l2_fmt,
+        .avcodec = avcodec,
+    };
+    size_t len = FF_ARRAY_ELEMS(fmt_map);
+    struct fmt_conversion *item;
+
+    item = lfind(&key, fmt_map, &len, sizeof(fmt_map[0]), match_codecfmt);
+    if (item)
+        return item->avfmt;
+
+    return AV_PIX_FMT_NONE;
+}

libavcodec/v4l2_fmt.h

+/*
+ * V4L2 format helper functions
+ *
+ * Copyright (C) 2017 Alexis Ballier <aballier@gentoo.org>
+ * Copyright (C) 2017 Jorge Ramirez <jorge.ramirez-ortiz@linaro.org>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef AVCODEC_V4L2_FMT_H
+#define AVCODEC_V4L2_FMT_H
+
+#include "libavcodec/avcodec.h"
+#include "libavutil/pixfmt.h"
+
+enum AVPixelFormat ff_v4l2_format_v4l2_to_avfmt(uint32_t v4l2_fmt, enum AVCodecID avcodec);
+uint32_t ff_v4l2_format_avcodec_to_v4l2(enum AVCodecID avcodec);
+uint32_t ff_v4l2_format_avfmt_to_v4l2(enum AVPixelFormat avfmt);
+
+#endif /* AVCODEC_V4L2_FMT_H*/

libavcodec/v4l2_m2m.h

+/*
+ * V4L2 mem2mem helper functions
+ *
+ * Copyright (C) 2017 Alexis Ballier <aballier@gentoo.org>
+ * Copyright (C) 2017 Jorge Ramirez <jorge.ramirez-ortiz@linaro.org>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef AVCODEC_V4L2_M2M_H
+#define AVCODEC_V4L2_M2M_H
+
+#include <semaphore.h>
+#include <unistd.h>
+#include <dirent.h>
+#include "libavcodec/avcodec.h"
+#include "v4l2_context.h"
+
+#define container_of(ptr, type, member) ({ \
+        const __typeof__(((type *)0)->member ) *__mptr = (ptr); \
+        (type *)((char *)__mptr - offsetof(type,member) );})
+
+#define V4L_M2M_DEFAULT_OPTS \
+    { "num_output_buffers", "Number of buffers in the output context",\
+        OFFSET(output.num_buffers), AV_OPT_TYPE_INT, { .i64 = 16 }, 6, INT_MAX, FLAGS }
+
+typedef struct V4L2m2mContext
+{
+    AVClass *class;
+    char devname[PATH_MAX];
+    int fd;
+
+    /* the codec context queues */
+    V4L2Context capture;
+    V4L2Context output;
+
+    /* refcount of buffers held by the user */
+    atomic_uint refcount;
+
+    /* dynamic stream reconfig */
+    AVCodecContext *avctx;
+    sem_t refsync;
+    int reinit;
+
+    /* null frame/packet received */
+    int draining;
+} V4L2m2mContext;
+
+/**
+ * Probes the video nodes looking for the required codec capabilities.
+ *
+ * @param[in] ctx The AVCodecContext instantiated by the encoder/decoder.
+ *
+ * @returns 0 if a driver is found, a negative number otherwise.
+ */
+int ff_v4l2_m2m_codec_init(AVCodecContext *avctx);
+
+/**
+ * Releases all the codec resources if all AVBufferRefs have been returned to the
+ * ctx. Otherwise keep the driver open.
+ *
+ * @param[in] The AVCodecContext instantiated by the encoder/decoder.
+ *
+ * @returns 0
+ *
+ */
+int ff_v4l2_m2m_codec_end(AVCodecContext *avctx);
+
+/**
+ * Reinitializes the V4L2m2mContext when the driver cant continue processing
+ * with the capture parameters.
+ *
+ * @param[in] ctx The V4L2m2mContext instantiated by the encoder/decoder.
+ *
+ * @returns 0 in case of success, negative number otherwise
+ */
+int ff_v4l2_m2m_codec_reinit(V4L2m2mContext *ctx);
+
+/**
+ * Reinitializes the V4L2m2mContext when the driver cant continue processing
+ * with the  any of the current V4L2Contexts (ie, changes in output and capture).
+ *
+ * @param[in] ctx The V4L2m2mContext instantiated by the encoder/decoder.
+ *
+ * @returns 0 in case of success, negative number otherwise
+ */
+int ff_v4l2_m2m_codec_full_reinit(V4L2m2mContext *ctx);
+
+#endif /* AVCODEC_V4L2_M2M_H */

libavcodec/v4l2_m2m_dec.c

+/*
+ * V4L2 mem2mem decoders
+ *
+ * Copyright (C) 2017 Alexis Ballier <aballier@gentoo.org>
+ * Copyright (C) 2017 Jorge Ramirez <jorge.ramirez-ortiz@linaro.org>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <linux/videodev2.h>
+#include <sys/ioctl.h>
+#include "libavutil/pixfmt.h"
+#include "libavutil/pixdesc.h"
+#include "libavutil/opt.h"
+#include "libavcodec/avcodec.h"
+#include "libavcodec/decode.h"
+
+#include "v4l2_context.h"
+#include "v4l2_m2m.h"
+#include "v4l2_fmt.h"
+
+static int v4l2_try_start(AVCodecContext *avctx)
+{
+    V4L2m2mContext *s = avctx->priv_data;
+    V4L2Context *const capture = &s->capture;
+    V4L2Context *const output = &s->output;
+    struct v4l2_selection selection;
+    int ret;
+
+    /* 1. start the output process */
+    if (!output->streamon) {
+        ret = ff_v4l2_context_set_status(output, VIDIOC_STREAMON);
+        if (ret < 0) {
+            av_log(avctx, AV_LOG_DEBUG, "VIDIOC_STREAMON on output context\n");
+            return ret;
+        }
+    }
+
+    if (capture->streamon)
+        return 0;
+
+    /* 2. get the capture format */
+    capture->format.type = capture->type;
+    ret = ioctl(s->fd, VIDIOC_G_FMT, &capture->format);
+    if (ret) {
+        av_log(avctx, AV_LOG_WARNING, "VIDIOC_G_FMT ioctl\n");
+        return ret;
+    }
+
+    /* 2.1 update the AVCodecContext */
+    avctx->pix_fmt = ff_v4l2_format_v4l2_to_avfmt(capture->format.fmt.pix_mp.pixelformat, AV_CODEC_ID_RAWVIDEO);
+    capture->av_pix_fmt = avctx->pix_fmt;
+
+    /* 3. set the crop parameters */
+    selection.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
+    selection.r.height = avctx->coded_height;
+    selection.r.width = avctx->coded_width;
+    ret = ioctl(s->fd, VIDIOC_S_SELECTION, &selection);
+    if (!ret) {
+        ret = ioctl(s->fd, VIDIOC_G_SELECTION, &selection);
+        if (ret) {
+            av_log(avctx, AV_LOG_WARNING, "VIDIOC_G_SELECTION ioctl\n");
+        } else {
+            av_log(avctx, AV_LOG_DEBUG, "crop output %dx%d\n", selection.r.width, selection.r.height);
+            /* update the size of the resulting frame */
+            capture->height = selection.r.height;
+            capture->width  = selection.r.width;
+        }
+    }
+
+    /* 4. init the capture context now that we have the capture format */
+    if (!capture->buffers) {
+        ret = ff_v4l2_context_init(capture);
+        if (ret) {
+            av_log(avctx, AV_LOG_DEBUG, "can't request output buffers\n");
+            return ret;
+        }
+    }
+
+    /* 5. start the capture process */
+    ret = ff_v4l2_context_set_status(capture, VIDIOC_STREAMON);
+    if (ret) {
+        av_log(avctx, AV_LOG_DEBUG, "VIDIOC_STREAMON, on capture context\n");
+        return ret;
+    }
+
+    return 0;
+}
+
+static int v4l2_prepare_decoder(V4L2m2mContext *s)
+{
+    struct v4l2_event_subscription sub;
+    V4L2Context *output = &s->output;
+    int ret;
+
+    /**
+     * requirements
+     */
+    memset(&sub, 0, sizeof(sub));
+    sub.type = V4L2_EVENT_SOURCE_CHANGE;
+    ret = ioctl(s->fd, VIDIOC_SUBSCRIBE_EVENT, &sub);
+    if ( ret < 0) {
+        if (output->height == 0 || output->width == 0) {
+            av_log(s->avctx, AV_LOG_ERROR,
+                "the v4l2 driver does not support VIDIOC_SUBSCRIBE_EVENT\n"
+                "you must provide codec_height and codec_width on input\n");
+            return ret;
+        }
+    }
+
+    return 0;
+}
+
+static int v4l2_receive_frame(AVCodecContext *avctx, AVFrame *frame)
+{
+    V4L2m2mContext *s = avctx->priv_data;
+    V4L2Context *const capture = &s->capture;
+    V4L2Context *const output = &s->output;
+    AVPacket avpkt = {0};
+    int ret;
+
+    ret = ff_decode_get_packet(avctx, &avpkt);
+    if (ret < 0 && ret != AVERROR_EOF)
+        return ret;
+
+    if (s->draining)
+        goto dequeue;
+
+    ret = ff_v4l2_context_enqueue_packet(output, &avpkt);
+    if (ret < 0) {
+        if (ret != AVERROR(ENOMEM))
+           return ret;
+        /* no input buffers available, continue dequeing */
+    }
+
+    if (avpkt.size) {
+        ret = v4l2_try_start(avctx);
+        if (ret)
+            return 0;
+    }
+
+dequeue:
+    return ff_v4l2_context_dequeue_frame(capture, frame);
+}
+
+static av_cold int v4l2_decode_init(AVCodecContext *avctx)
+{
+    V4L2m2mContext *s = avctx->priv_data;
+    V4L2Context *capture = &s->capture;
+    V4L2Context *output = &s->output;
+    int ret;
+
+    /* if these dimensions are invalid (ie, 0 or too small) an event will be raised
+     * by the v4l2 driver; this event will trigger a full pipeline reconfig and
+     * the proper values will be retrieved from the kernel driver.
+     */
+    output->height = capture->height = avctx->coded_height;
+    output->width = capture->width = avctx->coded_width;
+
+    output->av_codec_id = avctx->codec_id;
+    output->av_pix_fmt  = AV_PIX_FMT_NONE;
+
+    capture->av_codec_id = AV_CODEC_ID_RAWVIDEO;
+    capture->av_pix_fmt = avctx->pix_fmt;
+
+    ret = ff_v4l2_m2m_codec_init(avctx);
+    if (ret) {
+        av_log(avctx, AV_LOG_ERROR, "can't configure decoder\n");
+        return ret;
+    }
+
+    return v4l2_prepare_decoder(s);
+}
+
+#define OFFSET(x) offsetof(V4L2m2mContext, x)
+#define FLAGS AV_OPT_FLAG_VIDEO_PARAM | AV_OPT_FLAG_DECODING_PARAM
+
+static const AVOption options[] = {
+    V4L_M2M_DEFAULT_OPTS,
+    { "num_capture_buffers", "Number of buffers in the capture context",
+        OFFSET(capture.num_buffers), AV_OPT_TYPE_INT, {.i64 = 20}, 20, INT_MAX, FLAGS },
+    { NULL},
+};
+
+#define M2MDEC(NAME, LONGNAME, CODEC, bsf_name) \
+static const AVClass v4l2_m2m_ ## NAME ## _dec_class = {\
+    .class_name = #NAME "_v4l2_m2m_decoder",\
+    .item_name  = av_default_item_name,\
+    .option     = options,\
+    .version    = LIBAVUTIL_VERSION_INT,\
+};\
+\
+AVCodec ff_ ## NAME ## _v4l2m2m_decoder = { \
+    .name           = #NAME "_v4l2m2m" ,\
+    .long_name      = NULL_IF_CONFIG_SMALL("V4L2 mem2mem " LONGNAME " decoder wrapper"),\
+    .type           = AVMEDIA_TYPE_VIDEO,\
+    .id             = CODEC ,\
+    .priv_data_size = sizeof(V4L2m2mContext),\
+    .priv_class     = &v4l2_m2m_ ## NAME ## _dec_class,\
+    .init           = v4l2_decode_init,\
+    .receive_frame  = v4l2_receive_frame,\
+    .close          = ff_v4l2_m2m_codec_end,\
+    .bsfs           = bsf_name, \
+};
+
+M2MDEC(h264,  "H.264", AV_CODEC_ID_H264,       "h264_mp4toannexb");
+M2MDEC(hevc,  "HEVC",  AV_CODEC_ID_HEVC,       "hevc_mp4toannexb");
+M2MDEC(mpeg1, "MPEG1", AV_CODEC_ID_MPEG1VIDEO, NULL);
+M2MDEC(mpeg2, "MPEG2", AV_CODEC_ID_MPEG2VIDEO, NULL);
+M2MDEC(mpeg4, "MPEG4", AV_CODEC_ID_MPEG4,      NULL);
+M2MDEC(h263,  "H.263", AV_CODEC_ID_H263,       NULL);
+M2MDEC(vc1 ,  "VC1",   AV_CODEC_ID_VC1,        NULL);
+M2MDEC(vp8,   "VP8",   AV_CODEC_ID_VP8,        NULL);
+M2MDEC(vp9,   "VP9",   AV_CODEC_ID_VP9,        NULL);