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Topic: Frequency and Nº of channels on low bitrates? (Read 3983 times) previous topic - next topic
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Frequency and Nº of channels on low bitrates?

I am going to encode some of my DVDs for playback on devices such as uDCDivX (MPEG4 player for the Sega Dreamcast) and would like to know what would you recommend me to set the frequency and number of channels for the following bitrates: 96,80,64,48 and 32kbps. I know that Ogg vorbis and especially HE-AAC would be much better choices at these bitrates, but I'm stuck with MP3. Also, the reason I'm asking what frequency should I use is because I'd rather change it using SSRC than letting the LAME encoder do it.

Frequency and Nº of channels on low bitrates?

Reply #1 –
I'm not sure what you mean by the number of channels (MP3 supports stereo & mono only), if the way of encoding, use joint-stereo for stereo, or mono if you don't care about stereo (it will give you probably imperceptably better sound quality, but will be mono). As for frequency, LAME presets certain resampling to certain VBR modes. If you're going to use CBR or ABR you'll have to check these for yourself (encode something at certain CBR or ABR bitrate and you'll see to what frequency it was resampled).

Frequency and Nº of channels on low bitrates?

Reply #2 –
Quote
I'm not sure what you mean by the number of channels (MP3 supports stereo & mono only), if the way of encoding, use joint-stereo for stereo, or mono if you don't care about stereo (it will give you probably imperceptably better sound quality, but will be mono). As for frequency, LAME presets certain resampling to certain VBR modes. If you're going to use CBR or ABR you'll have to check these for yourself (encode something at certain CBR or ABR bitrate and you'll see to what frequency it was resampled).
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By number of channels I mean stereo or mono. About your reply to my question about samplerate, I'll quote myself: "the reason I'm asking what frequency should I use is because I'd rather change it using SSRC than letting the LAME encoder do it."

Frequency and Nº of channels on low bitrates?

Reply #3 –
For the sampling rate, I'd suggest you to run lame with your target settings, and check the resampling value used by Lame. Then you can resample to this value prior to encoding.

Regarding the number of channels, under 96kbps it is a matter of personnal preference.

Frequency and Nº of channels on low bitrates?

Reply #4 –
Quote
For the sampling rate, I'd suggest you to run lame with your target settings, and check the resampling value used by Lame. Then you can resample to this value prior to encoding.

Regarding the number of channels, under 96kbps it is a matter of personnal preference.
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Ok, ok, I'll check out what LAME resamples to the stream to. About the mono vs stereo, I know it depends on the hearing of each person, but since my hearing is pretty crappy I wanted to encode something that people with good hearing would find at least tolerable, that's why I want your opinions.

Frequency and Nº of channels on low bitrates?

Reply #5 –
If someone has decent hearing he/she won't be pleased with mono encodes at 96kbps, unless they're legally deaf on one ear and half-deaf on the second ear. If target hardware supports VBR and there's no disk-space or bandwidth issues then there's no reason not to use presets with higher bitrates. You won't gain that much with SSRC resampling as you'll lose with low bitrates and converting stereo to mono. I'd say do the encodes at these 96kbps (ABR) at least, keep them (joint-)stereo, and use frequency which LAME defaults to.

Frequency and Nº of channels on low bitrates?

Reply #6 –
I found out that the device I'll mainly be playing this on only supports mono sound, although it does support VBR. I guess you're right about saying the benefits of manual SSRC resampling will be lost at such low bitrates, so that leaves with only one question: what would you say is the bitrate turning point where stereo (or joint stereo) starts to sound better than mono using v3.96.1?
 

Frequency and Nº of channels on low bitrates?

Reply #7 –
If your device supports mono only (strange stuff, MP3 player from 60s?), then encode it mono. As for the turning point, I don't think there's something like that. Generally, mono encodes will always have a tad higher sound quality than stereo ones because bits which won't be used for stereo information will be used for sound reproducition ...but they will be mono! Is mono/stereo a quality measurement for you? You can easily tell the difference between stereo & mono on no matter what bitrate - 320kbps or 32kbps, because one will be mono and another will be stereo.
I'm afraid noone will be able to honestly tell you what bitrate you should use, many people buy Microsoft's 64kbps-WMA-CD-alike bullshit, even more people find 128kbps tolerable, IMO good MP3s start at 160kbps, so it depends on your conditions out there what bitrate to choose. I'll just additionaly mention that you should stay away from CBR, use ABR on bitrates lower than 128-160kbps, and VBR on higher ones.