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

Robert Forsman bob.forsman at ericsson.com
Fri Mar 2 16:28:21 CET 2012

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.

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 think this is currently not a priority for the DASH team, but as
commercial servers start being deployed, expect it to start showing up
in user requests.

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