avcodec: add an AV1 frame split bitstream filter

This will be needed by the eventual native AV1 decoder.
Signed-off-by: James Almer <jamrial@gmail.com>

Changelog

@@ -22,6 +22,7 @@ version <next>:
 - removed libndi-newtek
 - agm decoder
 - KUX demuxer
+- AV1 frame split bitstream filter
 
 
 version 4.1:

configure

@@ -3076,6 +3076,7 @@ vc1_parser_select="vc1dsp"
 
 # bitstream_filters
 aac_adtstoasc_bsf_select="adts_header"
+av1_frame_split_select="cbs_av1"
 av1_metadata_bsf_select="cbs_av1"
 eac3_core_bsf_select="ac3_parser"
 filter_units_bsf_select="cbs"

libavcodec/Makefile

@@ -1068,6 +1068,7 @@ OBJS-$(CONFIG_XMA_PARSER)              += xma_parser.o
 # bitstream filters
 OBJS-$(CONFIG_AAC_ADTSTOASC_BSF)          += aac_adtstoasc_bsf.o mpeg4audio.o
 OBJS-$(CONFIG_AV1_METADATA_BSF)           += av1_metadata_bsf.o
+OBJS-$(CONFIG_AV1_FRAME_SPLIT_BSF)        += av1_frame_split_bsf.o
 OBJS-$(CONFIG_CHOMP_BSF)                  += chomp_bsf.o
 OBJS-$(CONFIG_DUMP_EXTRADATA_BSF)         += dump_extradata_bsf.o
 OBJS-$(CONFIG_DCA_CORE_BSF)               += dca_core_bsf.o

libavcodec/av1_frame_split_bsf.c

+/*
+ * Copyright (c) 2019 James Almer <jamrial@gmail.com>
+ *
+ * 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
+ */
+
+/**
+ * @file
+ * This bitstream filter splits AV1 Temporal Units into packets containing
+ * just one frame, plus any leading and trailing OBUs that may be present at
+ * the beginning or end, respectively.
+ *
+ * Temporal Units already containing only one frame will be passed through
+ * unchanged. When splitting can't be performed, the Temporal Unit will be
+ * passed through containing only the remaining OBUs starting from the first
+ * one after the last successfully split frame.
+ */
+
+#include "libavutil/avassert.h"
+
+#include "avcodec.h"
+#include "bsf.h"
+#include "cbs.h"
+#include "cbs_av1.h"
+
+typedef struct AV1FSplitContext {
+    AVPacket *buffer_pkt;
+    CodedBitstreamContext *cbc;
+    CodedBitstreamFragment temporal_unit;
+
+    int nb_frames;
+    int cur_frame;
+    int cur_frame_idx;
+    int last_frame_idx;
+} AV1FSplitContext;
+
+static int av1_frame_split_filter(AVBSFContext *ctx, AVPacket *out)
+{
+    AV1FSplitContext *s = ctx->priv_data;
+    CodedBitstreamFragment *td = &s->temporal_unit;
+    int i, ret;
+    int split = !!s->buffer_pkt->data;
+
+    if (!s->buffer_pkt->data) {
+        int nb_frames = 0;
+
+        ret = ff_bsf_get_packet_ref(ctx, s->buffer_pkt);
+        if (ret < 0)
+            return ret;
+
+        ret = ff_cbs_read_packet(s->cbc, td, s->buffer_pkt);
+        if (ret < 0) {
+            av_log(ctx, AV_LOG_WARNING, "Failed to parse temporal unit.\n");
+            goto passthrough;
+        }
+
+        for (i = 0; i < td->nb_units; i++) {
+            CodedBitstreamUnit *unit = &td->units[i];
+
+            if (unit->type == AV1_OBU_FRAME ||
+                unit->type == AV1_OBU_FRAME_HEADER)
+                nb_frames++;
+            else if (unit->type == AV1_OBU_TILE_LIST) {
+                av_log(ctx, AV_LOG_VERBOSE, "Large scale tiles are unsupported.\n");
+                goto passthrough;
+            }
+        }
+        if (nb_frames > 1) {
+            s->cur_frame = 0;
+            s->cur_frame_idx = s->last_frame_idx = 0;
+            s->nb_frames = nb_frames;
+            split = 1;
+        }
+    }
+
+    if (split) {
+        AV1RawFrameHeader *frame = NULL;
+        int cur_frame_type = -1, size = 0;
+
+        for (i = s->cur_frame_idx; i < td->nb_units; i++) {
+            CodedBitstreamUnit *unit = &td->units[i];
+
+            size += unit->data_size;
+            if (unit->type == AV1_OBU_FRAME) {
+                AV1RawOBU *obu = unit->content;
+
+                if (frame) {
+                    av_log(ctx, AV_LOG_WARNING, "Frame OBU found when Tile data for a "
+                                                "previous frame was expected.\n");
+                    goto passthrough;
+                }
+
+                frame = &obu->obu.frame.header;
+                cur_frame_type = obu->header.obu_type;
+                s->last_frame_idx = s->cur_frame_idx;
+                s->cur_frame_idx  = i + 1;
+                s->cur_frame++;
+
+                // split here unless it's the last frame, in which case
+                // include every trailing OBU
+                if (s->cur_frame < s->nb_frames)
+                    break;
+            } else if (unit->type == AV1_OBU_FRAME_HEADER) {
+                AV1RawOBU *obu = unit->content;
+
+                if (frame) {
+                    av_log(ctx, AV_LOG_WARNING, "Frame Header OBU found when Tile data for a "
+                                                "previous frame was expected.\n");
+                    goto passthrough;
+                }
+
+                frame = &obu->obu.frame_header;
+                cur_frame_type = obu->header.obu_type;
+                s->last_frame_idx = s->cur_frame_idx;
+                s->cur_frame++;
+
+                // split here if show_existing_frame unless it's the last
+                // frame, in which case include every trailing OBU
+                if (frame->show_existing_frame &&
+                    s->cur_frame < s->nb_frames) {
+                    s->cur_frame_idx = i + 1;
+                    break;
+                }
+            } else if (unit->type == AV1_OBU_TILE_GROUP) {
+                AV1RawOBU *obu = unit->content;
+                AV1RawTileGroup *group = &obu->obu.tile_group;
+
+                if (!frame || cur_frame_type != AV1_OBU_FRAME_HEADER) {
+                    av_log(ctx, AV_LOG_WARNING, "Unexpected Tile Group OBU found before a "
+                                                "Frame Header.\n");
+                    goto passthrough;
+                }
+
+                if ((group->tg_end == (frame->tile_cols * frame->tile_rows) - 1) &&
+                    // include every trailing OBU with the last frame
+                    s->cur_frame < s->nb_frames) {
+                    s->cur_frame_idx = i + 1;
+                    break;
+                }
+            }
+        }
+        av_assert0(frame && s->cur_frame <= s->nb_frames);
+
+        ret = av_packet_ref(out, s->buffer_pkt);
+        if (ret < 0)
+            goto fail;
+
+        out->data = (uint8_t *)td->units[s->last_frame_idx].data;
+        out->size = size;
+
+        // skip the frame in the buffer packet if it's split successfully, so it's not present
+        // if the packet is passed through in case of failure when splitting another frame.
+        s->buffer_pkt->data += size;
+        s->buffer_pkt->size -= size;
+
+        if (!frame->show_existing_frame && !frame->show_frame)
+            out->pts = AV_NOPTS_VALUE;
+
+        if (s->cur_frame == s->nb_frames) {
+            av_packet_unref(s->buffer_pkt);
+            ff_cbs_fragment_reset(s->cbc, td);
+        }
+
+        return 0;
+    }
+
+passthrough:
+    av_packet_move_ref(out, s->buffer_pkt);
+
+    ret = 0;
+fail:
+    if (ret < 0) {
+        av_packet_unref(out);
+        av_packet_unref(s->buffer_pkt);
+    }
+    ff_cbs_fragment_reset(s->cbc, td);
+
+    return ret;
+}
+
+static const CodedBitstreamUnitType decompose_unit_types[] = {
+    AV1_OBU_TEMPORAL_DELIMITER,
+    AV1_OBU_SEQUENCE_HEADER,
+    AV1_OBU_FRAME_HEADER,
+    AV1_OBU_TILE_GROUP,
+    AV1_OBU_FRAME,
+};
+
+static int av1_frame_split_init(AVBSFContext *ctx)
+{
+    AV1FSplitContext *s = ctx->priv_data;
+    CodedBitstreamFragment *td = &s->temporal_unit;
+    int ret;
+
+    s->buffer_pkt = av_packet_alloc();
+    if (!s->buffer_pkt)
+        return AVERROR(ENOMEM);
+
+    ret = ff_cbs_init(&s->cbc, AV_CODEC_ID_AV1, ctx);
+    if (ret < 0)
+        return ret;
+
+    s->cbc->decompose_unit_types    = (CodedBitstreamUnitType*)decompose_unit_types;
+    s->cbc->nb_decompose_unit_types = FF_ARRAY_ELEMS(decompose_unit_types);
+
+    if (!ctx->par_in->extradata_size)
+        return 0;
+
+    ret = ff_cbs_read_extradata(s->cbc, td, ctx->par_in);
+    if (ret < 0)
+        av_log(ctx, AV_LOG_WARNING, "Failed to parse extradata.\n");
+
+    ff_cbs_fragment_reset(s->cbc, td);
+
+    return 0;
+}
+
+static void av1_frame_split_flush(AVBSFContext *ctx)
+{
+    AV1FSplitContext *s = ctx->priv_data;
+
+    av_packet_unref(s->buffer_pkt);
+    ff_cbs_fragment_reset(s->cbc, &s->temporal_unit);
+}
+
+static void av1_frame_split_close(AVBSFContext *ctx)
+{
+    AV1FSplitContext *s = ctx->priv_data;
+
+    av_packet_free(&s->buffer_pkt);
+    ff_cbs_fragment_free(s->cbc, &s->temporal_unit);
+    ff_cbs_close(&s->cbc);
+}
+
+static const enum AVCodecID av1_frame_split_codec_ids[] = {
+    AV_CODEC_ID_AV1, AV_CODEC_ID_NONE,
+};
+
+const AVBitStreamFilter ff_av1_frame_split_bsf = {
+    .name           = "av1_frame_split",
+    .priv_data_size = sizeof(AV1FSplitContext),
+    .init           = av1_frame_split_init,
+    .flush          = av1_frame_split_flush,
+    .close          = av1_frame_split_close,
+    .filter         = av1_frame_split_filter,
+    .codec_ids      = av1_frame_split_codec_ids,
+};

libavcodec/bitstream_filters.c

@@ -25,6 +25,7 @@
 #include "bsf.h"
 
 extern const AVBitStreamFilter ff_aac_adtstoasc_bsf;
+extern const AVBitStreamFilter ff_av1_frame_split_bsf;
 extern const AVBitStreamFilter ff_av1_metadata_bsf;
 extern const AVBitStreamFilter ff_chomp_bsf;
 extern const AVBitStreamFilter ff_dump_extradata_bsf;

libavcodec/version.h

@@ -28,7 +28,7 @@
 #include "libavutil/version.h"
 
 #define LIBAVCODEC_VERSION_MAJOR  58
-#define LIBAVCODEC_VERSION_MINOR  49
+#define LIBAVCODEC_VERSION_MINOR  50
 #define LIBAVCODEC_VERSION_MICRO 100
 
 #define LIBAVCODEC_VERSION_INT  AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \