[FFmpeg-user] audio is out of sync and "ALSA buffer xrun"

LANGLOIS Olivier PIS -EXT olivier.pis.langlois at transport.alstom.com
Tue Feb 18 18:02:37 CET 2014

If you want to have them, you need to recompile the kernel with this setting:

lano1106 at hpmini ~/dev/linux-ck/src/linux-3.12 $ zgrep SND_VERBOSE /proc/config.gz

You can use my numbers, it should give you some idea:

lano1106 at hpmini /proc/asound/card0/pcm0c/sub0 $ cat hw_params
format: S16_LE
subformat: STD
channels: 2
rate: 44100 (44100/1)
period_size: 11025
buffer_size: 22050

22050/44100 = 0.5 (yours could be smaller)


The rtmp handshake has 3 messages exchanges.

take the rtt from 'ping live-fra.twitch.tv', multiply by 3 and this value must be smaller than 0.5 or whatever you buffer_time is.

this server doesn't seem to reply to ICMP echo request so you can get some timing insight by recording your rtmp exchange with wireshark something like that.

> -----Original Message-----
> From: ffmpeg-user-bounces at ffmpeg.org [mailto:ffmpeg-user-
> bounces at ffmpeg.org] On Behalf Of YuGiOhJCJ Mailing-List
> Sent: Tuesday, February 18, 2014 11:44 AM
> To: FFmpeg user questions
> Subject: Re: [FFmpeg-user] audio is out of sync and "ALSA buffer xrun"
> It seems I have not the same file hierarchy than you in this folder:
> $ ls -l /proc/asound/card0/
> total 0
> -r--r--r-- 1 root root 0 Feb 18 17:42 codec#0
> -r--r--r-- 1 root root 0 Feb 18 17:42 id

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