Tsdemux latency

[Olivier Crête]

Hello,

On Mon, 2017-07-10 at 08:53 +0000, paolo perotinus wrote:
> 1) There's a hardcoded latency of 700ms in tsdemux.c: "#define
> TS_LATENCY (700 * GST_MSECOND)". However, the latency that I measured
> is about 300ms, then, what is the 700ms value? If I set it to a lower
> value (i.e: 50) and recompile nothing changes.

This is from the MPEG-TS specification, it corresponds to the maximum
space between two PCR values, it's a relatively unavoidable worse case.
You can set a lower latency on your pipeline with
gst_pipeline_set_latency(), but this can cause failures (the sink
dropping all the frames as late) if your stream is muxed at a higher
value.

> 2) Can I reduce the latency if I manually set the width and the
> height of the received stream, on the gst-launch-1.0 command? I tried
> with:  "gst-launch-1.0 -v souphttpsrc location=http://127.0.0.1:8080/
> stream.ts ! tsdemux name=demuxer demuxer. ! h264parse ! "video/x-
> h264,width=640,height=480" ! avdec_h264 ! autovideosink"  but nothing
> changes.
> 
> 3) Can I reduce the latency if I manually set the width and the
> height of the received stream on the C code? If so, which element
> should I add/modify for doing that?

The resolution changes nothing to that latency, it's entirely due to
the MPEG-TS specification.


-- 
Olivier Crête
olivier.crete at collabora.com
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