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Topic: A few questions (bit reservoir, CVBR vs TVBR, high frequency content) (Read 3151 times) previous topic - next topic
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A few questions (bit reservoir, CVBR vs TVBR, high frequency content)

I have a few questions regarding AAC:

  • Does AAC use bit reservoir, like MP3 does?
  • Possibly related to previous question: which encoding mode yields (in theory at least) higher audio quality (regardless of file size): CVBR (Apple encoder) at 320 or TVBR Q127?
  • Does AAC retain more of the high frequency content of the input file than some other codecs, like Vorbis or MP3?

Re: A few questions (bit reservoir, CVBR vs TVBR, high frequency content)

Reply #1
Possibly related to previous question: which encoding mode yields (in theory at least) higher audio quality (regardless of file size): CVBR (Apple encoder) at 320 or TVBR Q127?
No encoder is perfect, so your question doesn't make sense. Are you asking about the theoretical ideal (using some magically perfect encoder) or are you asking about real encoders?

Does AAC retain more of the high frequency content of the input file than some other codecs, like Vorbis or MP3?
Content retention depends on the encoder, not the format.

 

Re: A few questions (bit reservoir, CVBR vs TVBR, high frequency content)

Reply #2
No encoder is perfect, so your question doesn't make sense. Are you asking about the theoretical ideal (using some magically perfect encoder) or are you asking about real encoders?

I never said any encoder was perfect. I just asked which of the two specific encoder settings (using Apple's AAC encoder) I mentioned yielded higher quality output (and what would be the theoretical reasons for that).

Content retention depends on the encoder, not the format.
OK, maybe I should rephrase my question: does Apple or Nero AAC encoder (either one of them) retain more high frequency content than, say, AoTuV Vorbis encoder (at comparable bitrates/target quality levels)?

Re: A few questions (bit reservoir, CVBR vs TVBR, high frequency content)

Reply #3
No encoder is perfect, so your question doesn't make sense. Are you asking about the theoretical ideal (using some magically perfect encoder) or are you asking about real encoders?

I never said any encoder was perfect. I just asked which of the two specific encoder settings (using Apple's AAC encoder) I mentioned yielded higher quality output (and what would be the theoretical reasons for that).

Content retention depends on the encoder, not the format.
OK, maybe I should rephrase my question: does Apple or Nero AAC encoder (either one of them) retain more high frequency content than, say, AoTuV Vorbis encoder (at comparable bitrates/target quality levels)?

They'll all be pretty similar most likely, although I think Vorbis at least lets you choose the lowpass cutoff frequency.  FWIW though, this really shouldn't matter unless you are doing something very strange.

Re: A few questions (bit reservoir, CVBR vs TVBR, high frequency content)

Reply #4
CVBR will mostly leave you with higher bitrate and bigger files than TVBR. But i can't remember which mode gave had a higher max bitrate. 256 CVBR should be really enough, but if you have the space and really want to use. 256 CVBR < 320 kbps CBR < 320 kbps TVBR < 320 kbps CVBR.

Vorbis can save frequencies up to 192 kHz. AAC up to 96 kHz but there are no encoders for that. So if you have 96 kHz files and want to preserve the high frequencies Vorbis is the way to go. It's the only lossy codec i know that can do this. Your files will get a little bit bigger than the 44 kHz version of course.

 
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