[FFmpeg-user] Decklink with ffmpeg audio desync

Marton Balint cus at passwd.hu
Thu May 12 21:19:12 CEST 2016

On Thu, 12 May 2016, Dpto. Datos Television Costa Blanca wrote:

> El 11/05/2016 a las 23:42, Marton Balint escribió:
>> With -ar 44100 you are resampling the initial sample rate of the captured
>> source (48000) to 44100. You are also manually specifying a resample
>> filter with -af resample. Try your encoding without these options.
> I've removed both options yesterday (figured it out) and video/audio 
> still desyncing.
> The actual command is:
> ./ffmpeg -re -f decklink -i "DeckLink SDI 4K at 2" -c:v mpeg2video -pix_fmt
> yuv420p -aspect 16:9 -deinterlace -sc_threshold 1000000000 -b:v 3.5M
> -minrate:v 3.5M -maxrate:v 3.5M -bufsize:v 2.4M -acodec mp2 -ac 2 -b:a
> 128k-metadata service_name="TVT" -mpegts_service_id 123 -f mpegts
> udp://
> Just for info, the SDI input comes from a matrix that when switch betwen 
> sources have a little delay and ffmpeg return a NO INPUT SIGNAL DETECTED -> 
> Can the desync come from here?

Yes, it is possible. Also I noticed you are using -re, there is no need 
for it, you cannot read from the device faster than realtime.


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