Allow to set an audio codec per channel

[felipecrs]

OPUS is great and is the best audio codec hands down.

But sometimes we need other codecs. For example, legacy HLS (browser) players can only play AAC audio.

go2rtc can be used for that:

streams:
  my_cam:
    - rtsp://thingino:thingino@192.168.1.31/ch1
    - ffmpeg:my_cam#audio=aac

But this will invoke ffmpeg on the receiving end, which consumes CPU resources and (probably) adds some latency.

It would be great if we could have different audio codecs per channel, so that I could do something like this in go2rtc:

streams:
  my_cam:
    # ch1 would be set to send OPUS
    - rtsp://thingino:thingino@192.168.1.31/ch1
    # copy AAC audio track from my_cam_hd
    - rtsp://127.0.0.1:8554/my_cam_hd?audio=aac
  my_cam_hd:
    # ch0 would be set to send AAC
    - rtsp://thingino:thingino@192.168.1.31/ch0
    # copy OPUS audio track from my_cam
    - rtsp://127.0.0.1:8554/my_cam?audio=opus

Which would not require any transcoding. :)

[themactep]

So let's be clear, you are worried about resources on the receiving end which has at least 512mb of ram, and want to solve it shifting the load onto a tiny camera with virtually nonexisting resources which is already busy fetching data from the sensor and transcoding and sending them?

[felipecrs]

I thought the camera would have enough to handle it. I guess some of them would.

The receiving end could be a Raspberry Pi 3 with enough resources to handle AAC transcoding for few cameras, but not enough to handle it for let's say 16 cameras.

[gtxaspec]

interesting, @nschimme want to take a stab at this?

[themactep]

An average camera has 64mb or ram with half of it reserved for media. It barely can handle what it is intended to do.

[felipecrs]

I see. Dahua and Hikvision cameras has this feature, but they are often expensive. Maybe they have better hardware indeed.

[gtxaspec]

depends on the chip the vendor uses. X/A series chips (ingenic) have 128+MB ram, while L/LC/N chips, only 64mb :O
We always recommend 128MB/16MB units, but sometimes thats not what you already have. But I think this feature would be awesome anyway to have, i actually do this remotely using go2rtc, would be nice to see if we can optimize it on unit.

[nschimme]

Sorry, too preoccupied with other projects right now. I see @felipecrs is an engineer, he should take a stab at it ;-)

[felipecrs]

Guys, no rush at all. I'm not demanding anything.

@nschimme, lol sure. Everyone can, I guess, no need to be an engineer. But not being familiar with the project and code base certainly makes the bar higher for me.

[nschimme]

Haha, I said the same thing before I added the AAC and OPUS codecs :-P