Prevent Audio Bitstream in RTSP Stream

[vocm88]

Hi all!

I'm fairly new to vlc and rtsp streaming so I apologise if I'm overlooking something obvious.

I have a network IP camera streaming H264 encoded video with NO AUDIO. When I connect using VLC (version 1.1.9) and the appropriate RTSP mrl I receive video (which is fantastic).
However, when I WireShark or NetLimiter, I see that there are two subsessions established. One of the subsessions is for the video which has a bit rate matching the set bit rate on the network ip device, and I assume the other is audio
with a fairly constant bit rate of 65 [kbits/s]. VLC media information states that PCMU audio codec is being used with a sample rate of 8000, and I'm guessing each sample is 8 bytes which roughly makes up 65 [kbits/s]. I don't want to be decoding audio when I connect to RTSP stream.

Is there a way to:
- disable the audio stream, OR
- prevent connection to the audio port OR
- ensure a zero bit rate?

I have searched the VLC forums and haven't been able to find a similar post.
Any help would be greatly appreciated,
Voc

[Sébastien Escudier]

there is the vlc option --no-audio but it only disable audio output. VLC would still receive the audio rtsp subsession
I don't think there is an option to disable audio input in the rtsp module, this would need to be implemented.
Maybe you can disable audio in your camera ?

[vocm88]

Hi Sebastien, thanks for the quick reply!

To my knowledge, I have disabled audio from the network camera. If I connect through the browser interface provided by the manufacturers when the network is local, I get only the video bitstream in NetLimiter.
I guess that's because it's not using RTSP protocol. I have tried the "--no-audio" command line to no avail.

Thanks for your suggestions, I will try investigate this further, but if anyone has experienced something like this please let me know.
Kind regards,
Voc.

[Sébastien Escudier]

run vlc with full logs (-vv and if you are on windows you will have to use msys rxvt)
you will see rtsp requests. (or you can see this in wireshark)

If audio is enabled you wil see something like :
m=audio 0 RTP/AVP 97
and two SETUP request (two tracks)

If you disabled audio in your camera and if you still see audio in the rtsp dialogue, I would say your camera is broken.

[vocm88]

Hi Sebastien,

I did as you suggested, and sure enough two connections are still established. I also managed to get my hands on a different IP network camera which I configured to only display video, and I see only one bit stream in NetLimiter, which has a bit rate matching the video bit rate set on the device. This means I do indeed have a problem with my original camera.

Thanks a bunch for your help!
Voc.