[FFmpeg-user] H.264 with pcm_mulaw audio live RTSP streaming

George Andguladze gandguladze at hotmail.com
Thu Jan 18 14:30:31 EET 2018

> The following works here:
> $ ffmpeg -rtsp_transport tcp -i rtsp... -qscale 2 -acodec copy -y out.avi

Can confirm. And to think that I spent last 36 hours on this issue thinking I was recording the actual audio in the room. (the room was empty the whole time until just one hour ago).

> I am happy if somebody convinces me that there is a bug in FFmpeg (and not in the Hikvision server)!

As for the timestamps I am fairly certain that our customized Hikvision implementation is to blame - we actually have a physical mixer device that merges output from two-three different microphones (different language translations of what's happening in the room spoken by operators in separate rooms in real time) and diverts it to a single camera's audio output; so when the NVR receives the rtsp stream from the camera, it records this merged audio track with different languages spoken on it. Usually it's a combination of the actual language spoken in the room (with decreased volume) and an overlay translation to a different language. I can only assume that merging of these tracks by the mixer device produces unstable/unpredictable output in some way related to the format/timestamps. 
The same thing is true when I fetch the MPEG-TS stream from the NVR. 
However, it would not be the first time I have encountered a buggy environment when working with Hikvision's internal API.

Thank you for your help, I will try to provide any requested information regarding this stream or Hikvision NVR API in general if asked to for the ffmpeg community.

Kind regards
George A.

More information about the ffmpeg-user mailing list