hello community,

i have a aac 5.1 movie audiotrack that was muxxed in an 25fps .mkv (its 2hrs 89mb, vbr ~120-170kbps, seems he-aac because its small but relativ high kbps (channel coupling?)).
i want to transcode it to 23.976fps to muxx it to the ntsc version of the movie.

i searched alot for not so complicated version for fulfilling the task.
but it seems that it is only possible via commandline & neroAACenc/dec ?
i didnt even find a simple frontend that can import 5.1 aac..

or is there somewhere software that actually imports 5.1 aac and decodes it to a 5.1 wav (that would be a beginning, so i could import it to eg besweet, that does not load aac at all)?

if not, i thought the way like this:
1.) decode with neroAACdec.exe to 6 wavs.
2.) import wavs to besweet & transcode fps, save/mux to 5.1 aac again.

the thing is, i need help with the settings (like channelorder should of course not be lost, final encoding qual, etc).

thx

You shouldn't have to do any more than simply demux it from the existing stream and mux it into the new stream. I do this all the time with 5.1 ac3 from NTSC to PAL, no transcoding is necessary. Unless, of course, there is something about aac audio that I'm not understanding.

I assume that the audio wasn't encoded normally at the proper pitch and length but was in fact encoded as sped up from 24 to 25 fps?

.
sorry, i dont know what your muxing, but these are then certainly not movies with different fps.
if you have a pal movie its some minutes shorter than the ntsc movie because of the difference in playing speed, so you cant mux without cutting the audiotrack or it being to short.
maybe you refer to pal/ntsc to the different resolution, but not to the playing speed.

but this is offtopic.

no, there are simply different sources. the track is from a dvd-pal rip, i want to mux it into a dvd-ntsc rip.

Well, if OP doesn't mind using a PAL framerate, it should be fine musing it together at 25fps.

However, to change the audio you need to pitch it. I do it by adjusting the samplerate and resample as i mention in this thread.

However you will need another samplerate than the one I posted (due to my incompetence on the field).

You need to adjust samplerate to 46033 instead, but beware that you may have a slight glitch in the audio (about 6ms after 2 hours i think). I guess it's too small to worry about.

The DVD PAL movie will be of identical duration to the DVD NTSC movie. I reprocessed 'Cry, the Beloved Country' only the other day. NTSC rip, demux audio, reprocess video and convert to PAL 25fps, remux - perfect sync.

When you say "convert to PAL", what are you exactly reffering to? If you use the original NTSC audio with no processing and mux it in a container specified as 25fps, then audio will be out of sync - Exactly 4%!

You can't just think that you can change framerate without processing and not even without loss! (Technically that's only possible if the source is 2:2:2:2:2:2:2:2:2:2:2:3 pulldown'ed, but i have yet to see such source)

exact.

now can you please go back to my topic.
somebody can answer my questions?

Didn't you read my answer, or did it not satisfy you?

Well shmendrik, u dont have even transcode it Just download mkvtoolnix (mkvmerge). Load ntsc video file, and your new audio, uncheck old audio track. Light new audio track and go to: format specific options>>strech by, and paste: 25000/23976. Now audio will be remuxed (streched) to new play time (ntsc). No need to reencode it. This feature is designed for video and subtitles tracks, but works with some audio formats too. Write, if this works with 5.1 he aac.

Do you have any technical details on how the audio is processed in this mode? I dislike you say "stretch", but I hope you mean that the audio is resampled down to the correct pitch this way - Otherwise I would highly recommend NOT to use such a feature...

I do not have any details, but 4% is not such deal (??) I read that many video dvd's are processed in simple way (24fps>>....), so who knows if pitch is preserved on them.
And muxing process is reversible (i hope in this case too ).

edit: sorry double post

4% is indeed much. It's almost an entire key off.

Yes DVD's are processed in a simple way - That's speeding up/down the audio. Preserving pitch is impossible with acceptable quality - Some might be okay with it (but average Joe doesn't care about quality nowadays anyway).

I could not make mkvmerge stretch AC3 audio.

sorry, the thread gets a liitle confusing.
you mean adjusting the samplerate?
but that was my question in the first place HOW to adjust the rate for a 6ch aac?!
you just had the solution for wave? and it wasnt really resampled but only the header was changed?
or i didnt get it right... how does this help in my case?


this way actually seems like a "dirty" trick, because it works when played back in the final mkv,
but if you demux the track again, it has still the same length as the "non-stretched" source aac.
so mkvmerge just writes an information in the mkv, but actually doesnt touch the audiotrack (and doesnt really stretch it physically).
but as i said again, HOW to really stretch this 6ch aac (like besweet really stretches eg a mp3 if you choose fps conversion) with reencoding it?

Well, Ac3 actually belongs to formats that are not "strechable" (at this time )



Because changing samplerate, you can adjust wrong pitch ?



Uhm, thats the power of this tool. This is the way: no procesing on audio track needed and you still have untouched stream.



Dont know

Enjoy
http://reclock.free.fr/

This DS filter, "Reclock" is what your looking for i think.

no.

You must have Nero 7 or Sonic audio decoder installed for AAC decoding with eac3to. NeroAACenc must be in the same directory as eac3to for encoding.


...will probably also work.

i have no intention to install the bloated nero.
is there a way/download to install just the aac direct show filter?


sounds good, but i get the error message: moov box not found.

Well, my plan were to reencode - So I decode the audio first, leaving me one multichannel wav file. Then I patch it's header to play back at a certain speed (samplerate). Then I use a good samplerate converter to convert to a native format (back to 48000) - I use the PPHS DSP in foobar, but Audition/Cool Edit should be really good at this too. SSRC should not be able to deal with arbitrary samplerates. Maybe SRC works, but I have not tried it.

I must admit that I find the Reclock filter really interesting and hope that it alone will solve my issue.


That doesn't make much sense to me - Why would some formats work only?

Yes, if you adjust the playback samplerate, you adjust the speed, and because PAL titles are sped up 4%, you will be able to reverse this effect

No, and even if there was one, it would be illegal anyway...

Can you tell us more about your input file? What container (raw AAC, MP4, etc...)? Does it play in VLC/iTunes/Quicktime/foobar2000...? Try to decode it with those programs, then. Eac3to will accept a wav file, slow it down from 25fps to 23.976fps and encode it to AAC.

Im curious about it too, as it is very useful feature. You should ask author for answer.



Reclock is designed for systems that lack of smooth video playback. I dont know your issue, but audio features (its replacement for default directsound device) are just side effects
Here is forum, where you can find newest version, as old site is no longer updated.

Well I'm actually trying to achieve it's sideeffects. Reason (as mentioned in previously linked topic) is that I'm too often annoyed when I can hear that audio (a song etc) in PAL movies are pitched as they always are when they are filmed in US.

Since I'm transcoding all my DVD's to h264 anyway, I could as well do the audio tweaking, but if I could do this during playback it would be much easier for me

Shmendrick, I found solution thanks to Raiden help Actually i made small changes to his code.

First of all download from nero site free encoder/decoder NeroDigital. Unzip it to eac3to directory.
Then make text file encode.bat and paste code in it:



Now run it U can adjust quality/bitrate by last switch. 0.50 is default.

You are confusing neroaacenc with the large nero packages. Neroaacenc is just a small cli program you download and put in the same dir. Get it here.

Edit: Oh, I see it needs the filter for decoding... It's not illegal to install a trial version.

One disadvantage using this method is the reduced bit depth. You will just get a 16 bit wav file during decoding. Better off using eac3to directly.