[vlc-devel] FW: Can anyone help please?

Nigel Warburton warburton_nigel at hotmail.com
Sun Jan 10 14:16:50 CET 2010

Rémi et al,

Hi, and thanks for your reply. Sure not knowing exactly what the ulaw 
encoding in the following statement then I guess its difficult for me to 
understand whether something is wrong, or whether its a feature request:

"C:\Program Files\VideoLAN\VLC\vlc.exe" c:\3.wav --sout 

The last message from Lordnk sort of suggests that it exists but needs 
further tweeking, unfortunately there isnt a lot more informaton like the 
actual code changes and I presume that his changes were never included in a 
VLC release (again not sure how I would check).

Everyone suggests that this is an easy fix, but right now not sure what to 
do, ANY help please!!

I was able to get VLC to stream g711 correctly using an sout chain of 
transcode:rtp. VLC does not seem to read ulaw from file correctly, so a new 
demux was needed. In fact, VLC demuxes ulaw as standard pcm, so it reads the 
file completely off-target.

Creation of a new FrameInfo type for ulaw at the demux stage allowed to 
control the incoming byte stream chunk size, which then in turn would then 
send packets to the sout module(s) in the correct size and with the correct 
timestamp. Creation of a new packetizer for g711 over RTP allowed control of 
the Source Identifier and Timestamp formats.

The end result on the wire is now:

  Code: Select all
    0.019982 ->    RTP PT=ITU-T G.711 PCMU, 
SSRC=0x852D, Seq=38586, Time=4941928
    0.020000 ->    RTP PT=ITU-T G.711 PCMU, 
SSRC=0x852D, Seq=38587, Time=4942088
    0.019986 ->    RTP PT=ITU-T G.711 PCMU, 
SSRC=0x852D, Seq=38588, Time=4942248
    0.019990 ->    RTP PT=ITU-T G.711 PCMU, 
SSRC=0x852D, Seq=38589, Time=4942408

----- Original Message ----- 
From: "Rémi Denis-Courmont" <remi at remlab.net>
To: <vlc-devel at videolan.org>
Cc: "Nigel Warburton" <warburton_nigel at hotmail.com>
Sent: Saturday, January 09, 2010 5:45 PM
Subject: Re: [vlc-devel] FW: Can anyone help please?


Le jeudi 7 janvier 2010 21:46:43 Nigel Warburton, vous avez écrit :
> Basically I was looking at using VLC to steam uLaw at 20ms so that it 
> could
>  be received by a Cisco IP Phone. Today the VLC player does not seem to
>  support it although I have seen a number of requests for support.

Those are not requests for support. Those are requests for a new feature.

> So that leaves me a bit stuck between waiting to see if this feature comes
>  into VLC and works, use something else, or see if anyone fancies to help
>  for a pat on the back, chocolate or cash.

As I already said, it does not seem particularly difficult, but it needs 
and motivation.

> I really think this fix would be really useful, today afaik 16ms isnt used
>  by any devices.

It's not really 16ms. It's just a side effect.

Rémi Denis-Courmont
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