[FFmpeg-user] mpeg-dash mux w/multiple representations? (multi-bitrate)

Mark Hassman mark at hassman.org
Thu Aug 13 16:03:02 CEST 2015


Does anyone know how to encode live mpeg-dash with multiple-bitrates?

I can create multiple outputs with -s.. this works well for multi-bitrate
hls (f=hls) as .m3u8 files are independent and can be referenced by a master
.m3u8, but with mpeg-dash (f=dash), each output's .mpd is independent.
Instead, what's needed is a single .mpd with multiple representations.

Looking at dashenc.c - appears the mux is setup for this, but I have no idea
how to queue this within ffmpeg.
Relevant excerpt from dashenc.c:  (ffmpeg v2.7)
line 505:
   if (c->has_video) {
        avio_printf(out, "\t\t<AdaptationSet contentType=\"video\"
segmentAlignment=\"true\" bitstreamSwitching=\"true\">\n");
        for (i = 0; i < s->nb_streams; i++) {  <-- this will append multiple
            AVStream *st = s->streams[i];
            OutputStream *os = &c->streams[i];

            if (st->codec->codec_type != AVMEDIA_TYPE_VIDEO)

            avio_printf(out, "\t\t\t<Representation id=\"%d\"
mimeType=\"video/mp4\" codecs=\"%s\"%s width=\"%d\" height=\"%d\">\n", i,
os->codec_str, os->bandwidth_str, st->codec->width, st->codec->height);
            output_segment_list(&c->streams[i], out, c);
            avio_printf(out, "\t\t\t</Representation>\n");
        avio_printf(out, "\t\t</AdaptationSet>\n");

There's little documentation on ffmpeg mpeg-dash.

Can anyone help?


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