lavf: Add support for WebM Live Muxing

This patch adds support for WebM Live Muxing by adding a new WebM
Chunk muxer. It writes out live WebM Chunks which can be used for
playback using Live DASH Clients.

Please see muxers.texi for sample usage.
Signed-off-by: Vignesh Venkatasubramanian <vigneshv@google.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Changelog

@@ -14,6 +14,7 @@ version <next>:
 - MMAL-accelerated H.264 decoding
 - basic APNG encoder and muxer
 - unpack DivX-style packed B-frames in MPEG-4 bitstream filter
+- WebM Live Chunk Muxer
 
 
 version 2.6:

doc/muxers.texi

@@ -1268,4 +1268,47 @@ ffmpeg -f webm_dash_manifest -i video1.webm \
        manifest.xml
 @end example
 
+@section webm_chunk
+
+WebM Live Chunk Muxer.
+
+This muxer writes out WebM headers and chunks as separate files which can be
+consumed by clients that support WebM Live streams via DASH.
+
+@subsection Options
+
+This muxer supports the following options:
+
+@table @option
+@item chunk_start_index
+Index of the first chunk (defaults to 0).
+
+@item header
+Filename of the header where the initialization data will be written.
+
+@item audio_chunk_duration
+Duration of each audio chunk in milliseconds (defaults to 5000).
+@end table
+
+@subsection Example
+@example
+ffmpeg -f v4l2 -i /dev/video0 \
+       -f alsa -i hw:0 \
+       -map 0:0 \
+       -c:v libvpx-vp9 \
+       -s 640x360 -keyint_min 30 -g 30 \
+       -f webm_chunk \
+       -header webm_live_video_360.hdr \
+       -chunk_start_index 1 \
+       webm_live_video_360_%d.chk \
+       -map 1:0 \
+       -c:a libvorbis \
+       -b:a 128k \
+       -f webm_chunk \
+       -header webm_live_audio_128.hdr \
+       -chunk_start_index 1 \
+       -audio_chunk_duration 1000 \
+       webm_live_audio_128_%d.chk
+@end example
+
 @c man end MUXERS

libavformat/Makefile

@@ -238,7 +238,7 @@ OBJS-$(CONFIG_MATROSKA_DEMUXER)          += matroskadec.o matroska.o  \
 OBJS-$(CONFIG_MATROSKA_MUXER)            += matroskaenc.o matroska.o \
                                             isom.o avc.o hevc.o \
                                             flacenc_header.o avlanguage.o vorbiscomment.o wv.o \
-                                            webmdashenc.o
+                                            webmdashenc.o webm_chunk.o
 OBJS-$(CONFIG_MD5_MUXER)                 += md5enc.o
 OBJS-$(CONFIG_MGSTS_DEMUXER)             += mgsts.o
 OBJS-$(CONFIG_MICRODVD_DEMUXER)          += microdvddec.o subtitles.o
@@ -452,12 +452,13 @@ OBJS-$(CONFIG_WEBM_MUXER)                += matroskaenc.o matroska.o \
                                             isom.o avc.o hevc.o \
                                             flacenc_header.o avlanguage.o \
                                             wv.o vorbiscomment.o \
-                                            webmdashenc.o
+                                            webmdashenc.o webm_chunk.o
 OBJS-$(CONFIG_WEBM_DASH_MANIFEST_DEMUXER)+= matroskadec.o matroska.o  \
                                             isom.o rmsipr.o flac_picture.o \
                                             oggparsevorbis.o vorbiscomment.o \
                                             flac_picture.o replaygain.o
 OBJS-$(CONFIG_WEBM_DASH_MANIFEST_MUXER)  += webmdashenc.o matroska.o
+OBJS-$(CONFIG_WEBM_CHUNK_MUXER)          += webm_chunk.o matroska.o
 OBJS-$(CONFIG_WEBP_MUXER)                += webpenc.o
 OBJS-$(CONFIG_WEBVTT_DEMUXER)            += webvttdec.o subtitles.o
 OBJS-$(CONFIG_WEBVTT_MUXER)              += webvttenc.o

libavformat/allformats.c

@@ -316,6 +316,7 @@ void av_register_all(void)
     REGISTER_DEMUXER (WC3,              wc3);
     REGISTER_MUXER   (WEBM,             webm);
     REGISTER_MUXDEMUX(WEBM_DASH_MANIFEST, webm_dash_manifest);
+    REGISTER_MUXER   (WEBM_CHUNK,       webm_chunk);
     REGISTER_MUXER   (WEBP,             webp);
     REGISTER_MUXDEMUX(WEBVTT,           webvtt);
     REGISTER_DEMUXER (WSAUD,            wsaud);

libavformat/matroskaenc.c

@@ -120,6 +120,7 @@ typedef struct MatroskaMuxContext {
     int64_t cluster_time_limit;
     int is_dash;
     int dash_track_number;
+    int is_live;
 
     uint32_t chapter_id_offset;
     int wrote_chapters;
@@ -1412,7 +1413,9 @@ static int mkv_write_header(AVFormatContext *s)
     // reserve space for the duration
     mkv->duration = 0;
     mkv->duration_offset = avio_tell(pb);
-    put_ebml_void(pb, 11);                  // assumes double-precision float to be written
+    if (!mkv->is_live) {
+        put_ebml_void(pb, 11);              // assumes double-precision float to be written
+    }
     end_ebml_master(pb, segment_info);
 
     ret = mkv_write_tracks(s);
@@ -1436,7 +1439,7 @@ static int mkv_write_header(AVFormatContext *s)
             return ret;
     }
 
-    if (!s->pb->seekable)
+    if (!s->pb->seekable && !mkv->is_live)
         mkv_write_seekhead(pb, mkv->main_seekhead);
 
     mkv->cues = mkv_start_cues(mkv->segment_offset);
@@ -1955,7 +1958,9 @@ static int mkv_write_trailer(AVFormatContext *s)
         avio_seek(pb, currentpos, SEEK_SET);
     }
 
-    end_ebml_master(pb, mkv->segment);
+    if (!mkv->is_live) {
+        end_ebml_master(pb, mkv->segment);
+    }
     av_freep(&mkv->tracks);
     av_freep(&mkv->cues->entries);
     av_freep(&mkv->cues);
@@ -2019,6 +2024,7 @@ static const AVOption options[] = {
     { "cluster_time_limit",  "Store at most the provided number of milliseconds in a cluster.",                               OFFSET(cluster_time_limit), AV_OPT_TYPE_INT64, { .i64 = -1 }, -1, INT64_MAX, FLAGS },
     { "dash", "Create a WebM file conforming to WebM DASH specification", OFFSET(is_dash), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 1, FLAGS },
     { "dash_track_number", "Track number for the DASH stream", OFFSET(dash_track_number), AV_OPT_TYPE_INT, { .i64 = 1 }, 0, 127, FLAGS },
+    { "live", "Write files assuming it is a live stream.", OFFSET(is_live), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 1, FLAGS },
     { "allow_raw_vfw", "allow RAW VFW mode", OFFSET(allow_raw_vfw), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 1, FLAGS },
     { NULL },
 };

libavformat/version.h

@@ -30,7 +30,7 @@
 #include "libavutil/version.h"
 
 #define LIBAVFORMAT_VERSION_MAJOR 56
-#define LIBAVFORMAT_VERSION_MINOR  29
+#define LIBAVFORMAT_VERSION_MINOR  30
 #define LIBAVFORMAT_VERSION_MICRO 100
 
 #define LIBAVFORMAT_VERSION_INT AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \

libavformat/webm_chunk.c

+/*
+ * Copyright (c) 2015, Vignesh Venkatasubramanian
+ *
+ * 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 WebM Chunk Muxer
+ * The chunk muxer enables writing WebM Live chunks where there is a header
+ * chunk, followed by data chunks where each Cluster is written out as a Chunk.
+ */
+
+#include <float.h>
+#include <time.h>
+
+#include "avformat.h"
+#include "avio.h"
+#include "internal.h"
+
+#include "libavutil/avassert.h"
+#include "libavutil/log.h"
+#include "libavutil/opt.h"
+#include "libavutil/avstring.h"
+#include "libavutil/parseutils.h"
+#include "libavutil/mathematics.h"
+#include "libavutil/time.h"
+#include "libavutil/time_internal.h"
+#include "libavutil/timestamp.h"
+
+typedef struct WebMChunkContext {
+    const AVClass *class;
+    int chunk_start_index;
+    char *header_filename;
+    int chunk_duration;
+    int chunk_count;
+    int chunk_index;
+    uint64_t duration_written;
+    int prev_pts;
+    AVOutputFormat *oformat;
+    AVFormatContext *avf;
+} WebMChunkContext;
+
+static int chunk_mux_init(AVFormatContext *s)
+{
+    WebMChunkContext *wc = s->priv_data;
+    AVFormatContext *oc;
+    int ret;
+
+    ret = avformat_alloc_output_context2(&wc->avf, wc->oformat, NULL, NULL);
+    if (ret < 0)
+        return ret;
+    oc = wc->avf;
+
+    oc->interrupt_callback = s->interrupt_callback;
+    oc->max_delay          = s->max_delay;
+    av_dict_copy(&oc->metadata, s->metadata, 0);
+
+    oc->priv_data = av_mallocz(oc->oformat->priv_data_size);
+    if (!oc->priv_data) {
+        avio_close(oc->pb);
+        return AVERROR(ENOMEM);
+    }
+    *(const AVClass**)oc->priv_data = oc->oformat->priv_class;
+    av_opt_set_defaults(oc->priv_data);
+    av_opt_set_int(oc->priv_data, "dash", 1, 0);
+    av_opt_set_int(oc->priv_data, "cluster_time_limit", wc->chunk_duration, 0);
+    av_opt_set_int(oc->priv_data, "live", 1, 0);
+
+    oc->streams = s->streams;
+    oc->nb_streams = s->nb_streams;
+
+    return 0;
+}
+
+static int set_chunk_filename(AVFormatContext *s, int is_header)
+{
+    WebMChunkContext *wc = s->priv_data;
+    AVFormatContext *oc = wc->avf;
+    if (is_header) {
+        if (!wc->header_filename) {
+            return AVERROR(EINVAL);
+        }
+        av_strlcpy(oc->filename, wc->header_filename, strlen(wc->header_filename) + 1);
+    } else {
+        if (av_get_frame_filename(oc->filename, sizeof(oc->filename),
+                                  s->filename, wc->chunk_index) < 0) {
+            av_log(oc, AV_LOG_ERROR, "Invalid chunk filename template '%s'\n", s->filename);
+            return AVERROR(EINVAL);
+        }
+    }
+    return 0;
+}
+
+static int webm_chunk_write_header(AVFormatContext *s)
+{
+    WebMChunkContext *wc = s->priv_data;
+    AVFormatContext *oc = NULL;
+    int ret;
+
+    // DASH Streams can only have either one track per file.
+    if (s->nb_streams != 1) { return AVERROR_INVALIDDATA; }
+
+    wc->chunk_count = 0;
+    wc->chunk_index = wc->chunk_start_index;
+    wc->oformat = av_guess_format("webm", s->filename, "video/webm");
+    if (!wc->oformat)
+        return AVERROR_MUXER_NOT_FOUND;
+
+    ret = chunk_mux_init(s);
+    if (ret < 0)
+        return ret;
+    oc = wc->avf;
+    ret = set_chunk_filename(s, 1);
+    if (ret< 0)
+        return ret;
+    ret = avio_open2(&oc->pb, oc->filename, AVIO_FLAG_WRITE,
+                     &s->interrupt_callback, NULL);
+    if (ret < 0)
+        return ret;
+
+    oc->pb->seekable = 0;
+    ret = oc->oformat->write_header(oc);
+    if (ret < 0)
+        return ret;
+    avio_close(oc->pb);
+    return 0;
+}
+
+static int chunk_start(AVFormatContext *s)
+{
+    WebMChunkContext *wc = s->priv_data;
+    AVFormatContext *oc = wc->avf;
+    int ret;
+
+    ret = set_chunk_filename(s, 0);
+    if (ret < 0)
+        return ret;
+    wc->chunk_index++;
+    ret = avio_open2(&oc->pb, oc->filename, AVIO_FLAG_WRITE,
+                     &s->interrupt_callback, NULL);
+    if (ret < 0)
+        return ret;
+    oc->pb->seekable = 0;
+    return 0;
+}
+
+static int chunk_end(AVFormatContext *s)
+{
+    WebMChunkContext *wc = s->priv_data;
+    AVFormatContext *oc = wc->avf;
+    int ret;
+
+    if (wc->chunk_start_index == wc->chunk_index)
+        return 0;
+    // Flush the cluster in WebM muxer.
+    oc->oformat->write_packet(oc, NULL);
+    ret = avio_close(oc->pb);
+    if (ret < 0)
+        return ret;
+    wc->chunk_count++;
+    return 0;
+}
+
+static int webm_chunk_write_packet(AVFormatContext *s, AVPacket *pkt)
+{
+    WebMChunkContext *wc = s->priv_data;
+    AVFormatContext *oc = wc->avf;
+    AVStream *st = s->streams[pkt->stream_index];
+    int ret;
+
+    if (st->codec->codec_type == AVMEDIA_TYPE_AUDIO) {
+        wc->duration_written += av_rescale_q(pkt->pts - wc->prev_pts,
+                                             st->time_base,
+                                             (AVRational) {1, 1000});
+        wc->prev_pts = pkt->pts;
+    }
+
+    // For video, a new chunk is started only on key frames. For audio, a new
+    // chunk is started based on chunk_duration.
+    if ((st->codec->codec_type == AVMEDIA_TYPE_VIDEO &&
+         (pkt->flags & AV_PKT_FLAG_KEY)) ||
+        (st->codec->codec_type == AVMEDIA_TYPE_AUDIO &&
+         (pkt->pts == 0 || wc->duration_written >= wc->chunk_duration))) {
+        wc->duration_written = 0;
+        if ((ret = chunk_end(s)) < 0 || (ret = chunk_start(s)) < 0) {
+            goto fail;
+        }
+    }
+
+    if (st->codec->codec_type == AVMEDIA_TYPE_AUDIO && pkt->pts == 0) {
+        goto fail;
+    }
+    ret = oc->oformat->write_packet(oc, pkt);
+    if (ret < 0)
+        goto fail;
+
+fail:
+    if (ret < 0) {
+        oc->streams = NULL;
+        oc->nb_streams = 0;
+        avformat_free_context(oc);
+    }
+
+    return ret;
+}
+
+static int webm_chunk_write_trailer(AVFormatContext *s)
+{
+    WebMChunkContext *wc = s->priv_data;
+    AVFormatContext *oc = wc->avf;
+    oc->oformat->write_trailer(oc);
+    chunk_end(s);
+    oc->streams = NULL;
+    oc->nb_streams = 0;
+    avformat_free_context(oc);
+    return 0;
+}
+
+#define OFFSET(x) offsetof(WebMChunkContext, x)
+static const AVOption options[] = {
+    { "chunk_start_index",  "start index of the chunk", OFFSET(chunk_start_index), AV_OPT_TYPE_INT, {.i64 = 0}, 0, INT_MAX, AV_OPT_FLAG_ENCODING_PARAM },
+    { "header", "filename of the header where the initialization data will be written", OFFSET(header_filename), AV_OPT_TYPE_STRING, { 0 }, 0, 0, AV_OPT_FLAG_ENCODING_PARAM },
+    { "audio_chunk_duration", "duration of each chunk in milliseconds", OFFSET(chunk_duration), AV_OPT_TYPE_INT, {.i64 = 5000}, 0, INT_MAX, AV_OPT_FLAG_ENCODING_PARAM },
+    { NULL },
+};
+
+#if CONFIG_WEBM_CHUNK_MUXER
+static const AVClass webm_chunk_class = {
+    .class_name = "WebM Chunk Muxer",
+    .item_name  = av_default_item_name,
+    .option     = options,
+    .version    = LIBAVUTIL_VERSION_INT,
+};
+
+AVOutputFormat ff_webm_chunk_muxer = {
+    .name           = "webm_chunk",
+    .long_name      = NULL_IF_CONFIG_SMALL("WebM Chunk Muxer"),
+    .mime_type      = "video/webm",
+    .extensions     = "chk",
+    .flags          = AVFMT_NOFILE | AVFMT_GLOBALHEADER | AVFMT_NEEDNUMBER |
+                      AVFMT_TS_NONSTRICT | AVFMT_ALLOW_FLUSH,
+    .priv_data_size = sizeof(WebMChunkContext),
+    .write_header   = webm_chunk_write_header,
+    .write_packet   = webm_chunk_write_packet,
+    .write_trailer  = webm_chunk_write_trailer,
+    .priv_class     = &webm_chunk_class,
+};
+#endif