Downmixing and downsampling library?

2008-03-31 20:04:45

Hi guys, first post but I've been lurking these forums for some time now  I'm basically using a specific encoding library that is very picky on the input PCM data and requires it to be resampled/downmixed beforehand, hence I'm looking for a library that could downsample and downmix from 5.1 to stereo hopefully, but I'd settle for something that could downmix from stereo to mono. Any suggestions? I've looked at SSRC and SRC but it looks like those only resample and don't handle downmixing. As a last resort, I guess I could use the ACM, but I'd rather not use it unless necessary

Downmixing and downsampling library?

Reply #1 – 2008-04-01 06:09:52

Why not just interface with the SoX command line utility? It can handle the downmixing and resampling, with very good quality and performance.

Downmixing and downsampling library?

Reply #2 – 2008-04-01 14:01:45

Thanks for the suggestion, I'll look into the source. The reason I can't just interface with the command line util is because the downmixing and resampling needs to be done on a live stream, hence I have a live PCM feed that I need to downmix/resample and then send it over to the encoder. I'll see if I can use SoX, though I'd much prefer a library

Downmixing and downsampling library?

Reply #3 – 2008-04-03 02:39:06

So, you want to be the broadcaster? I use foobar2000 + Oddcast in combination with the Icecast server. foobar2000 can resample and downmix before the audio is sent to the encoder.

Downmixing and downsampling library?

Reply #4 – 2008-04-03 14:38:13

Yes Hancoque, I will be the source of the audio. I am not playing music from my PC but rather using a live capture. I already have the entire chain setup, and I've done a quick implementation yesterday using ACM. I'd rather use another library to do the downmixing/resampling (commercial is definitely an option), but I cannot use external tools to do this. Thanks for the suggestions guys!

Downmixing and downsampling library?

Reply #5 – 2008-04-03 22:06:59

Care to explain your chain? What's the server you use?

Downmixing and downsampling library?

Reply #6 – 2008-04-04 14:06:45

I do a live capture of the audio using a proprietary library (allows multi-channel capture), which I then must somehow resample/downmix based on requirements of the stream. I then feed this resampled/downmixed PCM stream into an AAC encoder, which spits out encoded frames that I then send over the network. This is all done in a single custom application. The limitations are that I cannot change the capture format, and the encoder does not downmix/resample. ACM works fine for now, but it's not ideal