I hear a lot about CBR and VBR; what’s wrong with ABR?, Was “MP3 ABR WHY NOT.” (shouting won’t make anyone likelier to reply) Options

[soylentgreen]

I have read numerous forums and articles about mp3 cbr and vbr, some swear by cbr others vbr, the debate just goes on and on. I,ve tried cbr 256, vbr 256, cbr 320, cbr 192 cbr etc and I cant hear any difference. My question is why bother with cbr or vbr, why dont people just go with MP3 ABR, would this not be the ideal compromise, or I am missing something, as there does seem to be lack of mp3 abr on offer as downloads from the likes of Napster etc.

[JJZolx]

Hope I don't get jumped on for reviving this thread, but the discussion is relevant to a question I had.

How well suited do you think ABR is for online streaming (in lieu of using plain CBR), such as for a radio station's 64, 128, 256 kbps feeds? My thinking is:

- ABR provides potentially higher sound quality at a given bitrate than CBR.

- If there's buffering on the client end (which I would expect in nearly all cases), then the variations in bitrate per frame will be absorbed. Anyone with a marginal connection would have nearly as much of a problem with underruns with CBR as with ABR.

[halb27]

... How well suited do you think ABR is for online streaming (in lieu of using plain CBR), such as for a radio station's 64, 128, 256 kbps feeds? My thinking is:

- ABR provides potentially higher sound quality at a given bitrate than CBR.

- If there's buffering on the client end (which I would expect in nearly all cases), then the variations in bitrate per frame will be absorbed. Anyone with a marginal connection would have nearly as much of a problem with underruns with CBR as with ABR.

An alternative with frame bitrates which are even better controlled is to use -Vx -b n -B N -F, for instance -V5 -b128 -B160 -F for the 128 kbps quality (definitely only 128 and 160 kbps frames), or -V0 -b 256 -B 256 -F for the 256 kbps quality (only 256 kbps frames).

[JJZolx]

An alternative with frame bitrates which are even better controlled is to use -Vx -b n -B N -F, for instance -V5 -b128 -B160 -F for the 128 kbps quality (definitely only 128 and 160 kbps frames), or -V0 -b 256 -B 256 -F for the 256 kbps quality (only 256 kbps frames).

But is there any good reason to limit the minimum bitrate of frames? If the goal is to keep overall bitrate below a certain level, I would think it only increases the overall bitrate unnecessarily. A frame that might be encoded at 32 kbps, for instance, would be forced to 128 kbps (in the first example). We wouldn't be trying to keep the stream at a 'near constant' rate, just trying to cap it.

[halb27]

Probably you're right, and streaming works well without the -F switch. For silence or near-silence, this would be favorable. Using -F and a -b setting close to the desired average bitrate has the welcome tendency of keeping bit reservoir larger however, which partially makes up for the restrictions of the -B switch in terms of quality.

This post has been edited by halb27: Jul 24 2012, 16:22