lavf: Add WebM DASH Manifest Muxer

This patch adds the ability to generate WebM DASH manifest XML using
ffmpeg. A sample command line would be as follows:

ffmpeg \
  -f webm_dash_manifest -i video1.webm \
  -f webm_dash_manifest -i video2.webm \
  -f webm_dash_manifest -i audio1.webm \
  -f webm_dash_manifest -i audio2.webm \
  -map 0 -map 1 -map 2 -map 3 \
  -c copy \
  -f webm_dash_manifest \
  -adaptation_sets “id=0,streams=0,1 id=1,streams=2,3” \
  manifest.xml

It works by exporting necessary fields as metadata tags in matroskadec
and use those values to write the appropriate XML fields as per the WebM
DASH Specification [1]. Some ideas are adopted from webm-tools project
[2].

[1]
https://sites.google.com/a/webmproject.org/wiki/adaptive-streaming/webm-dash-specification
[2]
https://chromium.googlesource.com/webm/webm-tools/+/master/webm_dash_manifest/Signed-off-by: Vignesh Venkatasubramanian <vigneshv@google.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Changelog

@@ -34,6 +34,7 @@ version <next>:
 - Image format auto-detection
 - LRC demuxer and muxer
 - Samba protocol (via libsmbclient)
+- WebM DASH Manifest muxer
 
 
 version 2.2:

RELEASE_NOTES

@@ -151,6 +151,7 @@
     • Image format auto-detection
     • LRC lyric file demuxer and muxer
     • Samba protocol (via libsmbclient)
+    • WebM DASH Manifest muxer
 
    ┌────────────────────────────┐
    │ libavfilter                │

doc/muxers.texi

@@ -1100,4 +1100,34 @@ Note: some codecs may need different options depending on the output format;
 the auto-detection of this can not work with the tee muxer. The main example
 is the @option{global_header} flag.
 
+@section webm_dash_manifest
+
+WebM DASH Manifest muxer.
+
+This muxer implements the WebM DASH Manifest specification to generate the DASH manifest XML.
+
+@subsection Options
+
+This muxer supports the following options:
+
+@table @option
+@item adaptation_sets
+This option has the following syntax: "id=x,streams=a,b,c id=y,streams=d,e" where x and y are the
+unique identifiers of the adaptation sets and a,b,c,d and e are the indices of the corresponding
+audio and video streams. Any number of adaptation sets can be added using this option.
+@end table
+
+@subsection Example
+@example
+ffmpeg -f webm_dash_manifest -i video1.webm \
+       -f webm_dash_manifest -i video2.webm \
+       -f webm_dash_manifest -i audio1.webm \
+       -f webm_dash_manifest -i audio2.webm \
+       -map 0 -map 1 -map 2 -map 3 \
+       -c copy \
+       -f webm_dash_manifest \
+       -adaptation_sets "id=0,streams=0,1 id=1,streams=2,3" \
+       manifest.xml
+@end example
+
 @c man end MUXERS

libavformat/Makefile

@@ -223,7 +223,8 @@ OBJS-$(CONFIG_MATROSKA_DEMUXER)          += matroskadec.o matroska.o  \
                                             flac_picture.o replaygain.o
 OBJS-$(CONFIG_MATROSKA_MUXER)            += matroskaenc.o matroska.o \
                                             isom.o avc.o hevc.o \
-                                            flacenc_header.o avlanguage.o vorbiscomment.o wv.o
+                                            flacenc_header.o avlanguage.o vorbiscomment.o wv.o \
+                                            webmdashenc.o
 OBJS-$(CONFIG_MD5_MUXER)                 += md5enc.o
 OBJS-$(CONFIG_MGSTS_DEMUXER)             += mgsts.o
 OBJS-$(CONFIG_MICRODVD_DEMUXER)          += microdvddec.o subtitles.o
@@ -432,7 +433,13 @@ OBJS-$(CONFIG_WC3_DEMUXER)               += wc3movie.o
 OBJS-$(CONFIG_WEBM_MUXER)                += matroskaenc.o matroska.o \
                                             isom.o avc.o hevc.o \
                                             flacenc_header.o avlanguage.o \
-                                            wv.o vorbiscomment.o
+                                            wv.o vorbiscomment.o \
+                                            webmdashenc.o
+OBJS-$(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_WEBVTT_DEMUXER)            += webvttdec.o subtitles.o
 OBJS-$(CONFIG_WEBVTT_MUXER)              += webvttenc.o
 OBJS-$(CONFIG_WSAUD_DEMUXER)             += westwood_aud.o

libavformat/allformats.c

@@ -307,6 +307,7 @@ void av_register_all(void)
     REGISTER_MUXDEMUX(WAV,              wav);
     REGISTER_DEMUXER (WC3,              wc3);
     REGISTER_MUXER   (WEBM,             webm);
+    REGISTER_MUXDEMUX(WEBM_DASH_MANIFEST, webm_dash_manifest);
     REGISTER_MUXDEMUX(WEBVTT,           webvtt);
     REGISTER_DEMUXER (WSAUD,            wsaud);
     REGISTER_DEMUXER (WSVQA,            wsvqa);

libavformat/version.h

@@ -30,7 +30,7 @@
 #include "libavutil/version.h"
 
 #define LIBAVFORMAT_VERSION_MAJOR 55
-#define LIBAVFORMAT_VERSION_MINOR 47
+#define LIBAVFORMAT_VERSION_MINOR 48
 #define LIBAVFORMAT_VERSION_MICRO 100
 
 #define LIBAVFORMAT_VERSION_INT AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \