[vlc-devel] Smooth Streaming, resolution switches (follow-up)

Frederic YHUEL fyhuel at viotech.net
Sat Mar 3 17:02:44 CET 2012

On Fri, Mar 2, 2012 at 4:28 PM, Robert Forsman <bob.forsman at ericsson.com> wrote:
> On Fri, 2 Mar 2012 09:38:22 -0500
> Frederic YHUEL <fyhuel at viotech.net> wrote:
>> Of course, I had to add support of fragmented MP4 to the MP4 demux,
>> before doing that. I hope I will be able to send a clean patch soon.
> Another thing that is coming down the pipe for DASH is unmultiplexed
> MP4 segments.  The one hardware player that I know of requires DASH
> files where the audio and video are in separate representations.  You
> can expect that the servers will generate this shape of DASH content
> (partly because I'm writing one) instead of the multiplexed sample
> files that have been used so far.

Like in Smooth Streaming, then.

> There are a couple of advantages of unmultiplexed audio and video: the
> ability to store multiple audio languages with less disk space; and the
> ability to switch video resolutions without rejiggering the audio
> pipeline, the ability to play only the audio without wasting bandwidth
> on video.
> The one gotcha is that you have to properly interpret the
> Representation at presentationTimeOffset attribute for proper A/V sync.
> A/V sync appears to be a trouble spot for free software.

I did not see any problems with Smooth Streaming, but maybe there are.
The MP4 demux basically sends (up to) 100 ms of video samples to the
decoder, then 100 ms of audio samples, and so on... what happens after
that is still black magic for me :-)


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