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Topic: LAME setting for movie audio encode (Read 3934 times) previous topic - next topic
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LAME setting for movie audio encode

Dibrom,

what LAME settings you suggest for movie audio encodings. I need bitrate about 100-120 kbps. And i think, is it posibble to achieve good quality with full stereo, cause I want to preserve phase information from AC-3's downmixed to Dolby Surround WAV's.

And is it better to go with samplerate 48KHz or 44KHz? If I resample with SSRC do I need to apply any type of dither? If yes which type?

Sorry for so much questions.

LAME setting for movie audio encode

Reply #1 –
Quote
Originally posted by Evaldas
what LAME settings you suggest for movie audio encodings. I need bitrate about 100-120 kbps.


--dm-preset 120 should do fairly well I think.

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And i think, is it posibble to achieve good quality with full stereo, cause I want to preserve phase information from AC-3's downmixed to Dolby Surround WAV's.


Full stereo at 100-120kbps is not going to get you very good quality.  For the most part I think joint stereo should still preserve some of this phase information, but I'm not absolutely certain.  If you really need to be sure this is kept intact, you are going to have to use a higher bitrate I think.

Quote
And is it better to go with samplerate 48KHz or 44KHz? If I resample with SSRC do I need to apply any type of dither? If yes which type?


I'd actually resample to 44.1khz.  LAME seems to have problems with 48khz files from time to time in the form of unusual pre-echo behavior (sometimes it's better than at 44.1khz but other times it's much worse).

For these kinds of bitrates I probably wouldn't dither.. more bits may be spent on added noise in the higher frequencies which you can't really afford.

LAME setting for movie audio encode

Reply #3 –
Interestingly enough, the idea I originally mentioned in that thread about something like --divx <bitrate> is now worked into the abr presets.  Same thing goes for the other idea I mentioned there, dynamic settings according to bitrate.

Much of that discussion is from quite awhile ago, but I still feel the same way in that using a low quality VBR setting to try and achieve low bitrates (in LAME at least) is not the way to go for movie encoding.  You either have to use less accurate masking (lower V setting) or you have to use a much higher ath to achieve this... both will lead to more artifacts.

Just thought I'd add that.  I still think ABR with --alt-preset <bitrate> is the way to go.  If a 2-pass vbr/abr mode ever gets implemented that would be even better but I don't think there are any plans to do such a thing.

Maybe the best solution of all though would be to use Vorbis if you don't mind a non-mp3 solution.  Quality at lower bitrates is going to be much better.

LAME setting for movie audio encode

Reply #4 –
Thanks for fast reply.
Quote
Originally posted by Dibrom
Just thought I'd add that.  I still think ABR with --alt-preset <bitrate> is the way to go.  If a 2-pass vbr/abr mode ever gets implemented that would be even better but I don't think there are any plans to do such a thing.

I assume you mean --dm-preset <bitrate>, as in the first your post in this thread.
Quote
Originally posted by Dibrom
I do not advise to use rev7 for anything else than --alt-preset standard.

Thus means, I need to use LAME 3.90 alpha 9 compile, not yours revision 7?

LAME setting for movie audio encode

Reply #5 –
Quote
Originally posted by Evaldas
I assume you mean --dm-preset <bitrate>, as in the first your post in this thread.


Yes.  Depending on which version you use.  Soon they will all be --alt-preset.

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Thus means, I need to use LAME 3.90 alpha 9 compile, not yours revision 7?


For now yes, I'd advise using the normal LAME build until I can solidify a few things with my build.  Theoretically you should be fine using my build but there have been a few reports of alt-preset insane behaving a bit differently and I haven't had a chance to look into this.  So just to be on the safe side..