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Topic: Ideas for a new nero aac encoding feature (Read 4100 times) previous topic - next topic
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Ideas for a new nero aac encoding feature

Merry Xmas to all!
In these days I was thinking about an interesting feature I'd like to have with nero aac codec.

Since, at a given bitrate usually we get the best quality with VBR, followed by 2-pass ABR, single pass ABR and CBR, and when I choose VBR encoding the bitrate can be vary a lot from track to track (obviously, since here the fixed parameter is the qualty);
I was thinking if it's possible to implement a new 2-pass encoding (I shold call it hybrid VBR-ABR mode), where the first pass consist in calculating the value of the q parameter (used in VBR encoding) that can give, with a good level of approximation (even 1-2 bps should be fine) the chosen bitrate, and the second pass do the VBR encoding with this calculated q-value.

I think this could be a safe way to get the best of both world, since the quality should be higher than the normal 2-pass ABR encoding.

Sorry for my bad English and sorry if I said something wrong

Thanks to the people that will give me an answer!

Ideas for a new nero aac encoding feature

Reply #1 –
I can think of only two good reasons to try to achieve a particular bitrate as close as possible - either the transmission of the data is bandwidth limited and you want to use as much of the bandwidth as you can without exceeding it, or else you want the file to be a particular size, regardless of the resultant quality.

What you are suggesting doesn't work for the former case since the bitrate could be too high for the bandwidth part of the time and use less than the available bandwidth the rest of the time. This situation is what cbr was made for.

As for the second case, you would be wasting bits on material that doesn't need it, and limiting the quality artificially on material that does.

Either way I don't see the sense in what you are asking for. Instead I would suggest a modified vbr mode in which you can set a lower and an upper bound for the overall bitrate. If the results using your normal q parameter fall withing this range you are done, else repeat with a higher or lower value as needed.

Ideas for a new nero aac encoding feature

Reply #2 –
Quote from: pdq on
I can think of only two good reasons to try to achieve a particular bitrate as close as possible - either the transmission of the data is bandwidth limited and you want to use as much of the bandwidth as you can without exceeding it, or else you want the file to be a particular size, regardless of the resultant quality.

What you are suggesting doesn't work for the former case since the bitrate could be too high for the bandwidth part of the time and use less than the available bandwidth the rest of the time. This situation is what cbr was made for.

As for the second case, you would be wasting bits on material that doesn't need it, and limiting the quality artificially on material that does.

Either way I don't see the sense in what you are asking for. Instead I would suggest a modified vbr mode in which you can set a lower and an upper bound for the overall bitrate. If the results using your normal q parameter fall withing this range you are done, else repeat with a higher or lower value as needed.



Well, if it certainly isn't a good choice for streaming purpose (as every VBR encoder), I think it would be fine for replace ABR 2-pass, achieving a better quality using the same target bitrate. I will appreciate this option when I have to encode my album to use with my DAP and I want to "optimize" its 2GB of space...