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>

1 files changed, 30 insertions, 0 deletions

diff --git a/doc/muxers.texi b/doc/muxers.texi
index dc2a08bbef..55e06a3437 100644
--- a/doc/muxers.texi
+++ b/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