[vlc-devel] Zero-latency VLC

[Rémi Denis-Courmont]

On Thu, 5 Jul 2012 10:15:17 +0100, Maurizio Sciglio
<maurizio.sciglio at gmail.com> wrote:
> Thanks David.
> 
> In my case I'm using x264 with the zerolatency settings for my encoding
> back-end.
> Being a RTSP/RTP stream, VLC is using the Live555 demux. Can anyone
confirm
> whether the parameters from the SDP descriptor would affect internal
> buffering and introduce latency? I went through the code of Live555 and
I
> couldn't find any obvious source of internal latency. Any suggestion? I
> also tried decreasing the Live555's RTP packet reorder size but I
couldn't
> notice any difference.

It should be obvious, but there is no such thing as zero latency in the
real world. In particular, RTP has intrinsic latency due to finite network
bandwidth, packetization time, and inter-packet arrival delay variance
(a.k.a. network jitter) - all three of these factors introduce latency even
if there is no packet reordering. Packet reordering only makes latency
worse.

That being said, there are also some components in VLC that do not
properly deal with low-latency cases. For instance, the audio output
assumes a latency of at least 40ms. To reduce VLC latency, you need to
investigate what is failing or introducing unecessary delay and fix it.
That means debugging and patching. I really don't think you can get stable
playback with less than 80ms with the current code base.

-- 
Rémi Denis-Courmont
Sent from my collocated server