MeGui + AAC questions

[Dem0n]

Hi guys,

I'm trying to shrink some of my large videos down from 1080 to 720 using MeGui. The video aspect is fine, But I'm not satisfied with only a few audio encoding options within MeGui. I'm wanting to encode my DTS(HD-MA etc.) and AC3 to AAC as I feel that byte for byte AAC sounds nearly transparent.
Instead of using Nero AAC though, I demux the video file and encode the DTS/AC3 track with either QAAC or FHG-AAC downmixed to two channel stereo at a bitrate of ~256KBs. I then encode the video and add the audio into an MKV.

My question is do synchronization issues between A/V happen often when remuxing seperate tracks? Will I need to alter the audio delay on most videos or is it usually as it was before demuxing?
On the two files that Ive tried so far, It's been ok but I don't want to finish my settings templates and begin chugging through my library recoding everything only to find out after hours of time spent, that some of the files are now out of sync?
Any help on that issue would be a help!

As I don't have a 5.1 surround audio system, Im quite happy to downmix my audio to stereo (Plus save space). Would QAAC or FHG-AAC do a better job in terms of bitrate and transparency than using AC3 or Vorbis? Are they efficient at encoding regular audio as opposed to standard music?

The main goal for me is to shrink files to DVD-5 size whilst aiming for transparency (That I'm personally satisfied with) on both A&V. If somebody could help or give some pointers on any of the issues above, I'll be very grateful! :)

[Asmodian]

My question is do synchronization issues between A/V happen often when remuxing separate tracks? Will I need to alter the audio delay on most videos or is it usually as it was before demuxing?

If there is a delay in the audio the demuxer should mention it (usually by appending it to the file name).

Would QAAC or FHG-AAC do a better job in terms of bitrate and transparency than using AC3 or Vorbis? Are they efficient at encoding regular audio as opposed to standard music?

AAC is a much more efficient in terms of bitrate/transparency than AC3 and is much more compatible than Vorbis. Quality of Vorbis vs. AAC is more debatable but I favor AAC.

[Dem0n]

Thanks for the reply Asmodian. I'll use AAC instead. In your opinion, Would there be a big perceived difference between Nero AAC and QAAC/FHG-AAC at bitrates around the ~256kbs mark? Is there any other way of encoding QAAC audio within MeGui or will I have to demux and re-encode as I have been doing?

[tebasuna51]

To know differences between AAC encoders at low bitrates you can see:

Public Multiformat Listening Test @~64 kbps[2011]. Nero/Apple HE-AAC, CELT, Vorbis (http://forum.doom9.org/showthread.php?t=160185)

Public AAC Listening Test @ ~96 kbps [July 2011]. Nero, Apple, Fraunhofer and CT AAC (http://forum.doom9.org/showthread.php?t=161957)

But with bitrates ~256 Kb/s, for stereo, is not possible listen differences to make test between this encoders. All are nearly transparent.

[Dem0n]

So theoretically would an audio track encoded with HE-AAC V1 at 192kbps with 6 channels retain more detail than the same track downmixed to stereo and encoded at 192kbps AAC-LC?

[Asmodian]

I use bit rates where both Nero/Apple sound the same to me (>128 for stereo).

I don't like HE-AAC much, it sounds ok a very low bit rates but LC-AAC sounds better and the difference in file size means nothing to me at this point.

HE-AAC will have better channel separation but will have dropped a lot of the audio detail to get down to 64kbps (stereo). LC-AAC at 192kbps (stereo) will be nicely transparent.

Others think HE-AAC at 64kbps sounds fine.

[Atak_Snajpera]

indeed he-aac 64kbps sounded ok before opus codec.

opus @64kbps already sounds better than he-aac@64kbps or mp3@128kbps in stereo and slightly worse than mp3@128kbps in joint stereo mode.

[Dem0n]

Thanks for the help, From what I understand Opus isn't fully supported within the Matroska Video container yet? I think I'll probably stick with AAC-LC @192/224 bitrates then :)