[FFmpeg-user] ffmpeg audio distortion using blackmagic

Marton Balint cus at passwd.hu
Sun Jul 22 22:10:58 EEST 2018

On Wed, 18 Jul 2018, Flumotion Support wrote:

> Hello everybody
> I have problems capturing a sdi flow with ffmpeg, I'm using a blackmagic
> mini recorder pro, after a while of working the capture the audio is
> distorted and the only way to fix it is to restart ffmpeg.
> this is my pipeline
> /usr/local/bin/ffmpeg -re -loglevel 48 -format_code pal -f decklink -i
> DeckLink Mini Recorder -audio_input embedded -video_input sdi -vcodec
> libx264 -crf 22 -preset:v veryfast -b:v 900k -pix_fmt yuv420p -acodec
> libfdk_aac -ab 64k -ar 48000 -ac 2 -s 640x360 -f flv rtmp://
> myserver.com:1935/test/live
> I add an audio capture that is distorted from the second 10.
> I will grow any help you can offer me.
> Thanks in advance
> King regards
>> croppedvideo.mp4
> <https://drive.google.com/a/flumotion.com/file/d/1R_pjUps2xkLYepeTxLIWKxqSy_qCnTF0/view?usp=drive_web>
The audio gets corrupted during the DVE effect. Maybe there is something 
in the SDI signal that the decklink card does not like. (I had similar 
audio corruption when the PAL signal was mixed by an NTSC signal by 
mistake for a few seconds) Try using a frame sync. You can also try the 
HDMI capture by buying a SDI to HDMI converter. And you can also try the 
BlackMagic support of course, as this is almost surely a BlackMagic issue.


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