AAC 5.1 causes jerky MKV playback everything, function, recently, actually

andy

Hi,

I recently transcoded a 448Kbps AC3 file to a 5.1 aac+ file (VBR 50-70 Kb/s) with Oagmachine. Now, when I mux the aac file with Mkvtoolnix into a MKV container, video playback seems very jerky and totally out of sync. When trying to mux the original AC3 file with my Xvid video, everything seems to play just fine, so I'm assuming that it isn't my machine that's too slow for decoding (PIII 1Ghz).
Ofcourse I've used the search function first, but it didn't come up with the stuff I was actually hoping for, so if this issue has been discussed before but I missed it somehow, could someone then please redirect me to it?? I hope to hear soon from you.

EDIT: I'm using CoreAAC Audio Decoder 1.0b9
Profile: AAC+SBR(ofcourse)
Samplerate: 22050-gt;44100 Hz
Channels: 6-gt;6
Bits per sample: 16
Bitrate: approxinately 229 Kbps

Mediaplayer: MPC 6.4.8.2

Thanks in advance,

Splashdriver

What is your procesor usage during playback with aac and ac3?

Also what are you using to decode XviD, and are you using any post processing?
A P3 1GHz is barely enough to decode XviD + HE-AAC 5.1 with minimal settings

You may wanna check this thread:
showthread.php?s=amp;threadid=77998

Originally posted by Splashdriver
Bitrate: approximately 229 Kbps
If you are aiming at this overall bitrate range for your AC-3 transcodings, you should rather use AAC LC (Low Complexity), not HE-AAC, because it needs much less CPU resources for multichannel playback (and also encoding). The sound will be similar or maybe even a little bit better, too (without SBR artifacts), because HE-AAC is rather meant to be used for even lower bitrates, i.e. below 200 kbps/6ch. You can find some recommendations for suitable FAAC encoder settings here.

At what bitrate do you guys consider that a 5.1 LC encode starts to sound better or retains more of the original audio information than a 5.1 HE encode (hans-jürgen, the thread you linked to doesn't answer exactly that)? Also, when transcoding from a 5.1 DTS source to 5.1 AAC, is it possible to equal or surpass the quality of an original 5.1 AC3?

I'm asking these questions because I'm about to back up a DVD that has both DTS and AC3 tracks and want to use the least possible audio bitrate so that I can make an anamorphic encode but would like as much audio quality as possible.

Originally posted by Chainmax
At what bitrate do you guys consider that a 5.1 LC encode starts to sound better or retains more of the original audio information than a 5.1 HE encode (hans-jürgen, the thread you linked to doesn't answer exactly that)?
There are no objective tests publicly available that would answer this question, so it's the best to test it for yourself. For example Nero seems to switch automatically to AAC LC somewhere above ~80 kbps/stereo VBR, but I don't know what Coding Technologies' codec uses for highest HE AAC bitrate or if it switches automatically at all.

Another important fact to consider besides the decoding complexity (not for MKV, but for the MP4 container) is if your next hardware decoder (DVD player, mobile phone etc.) will be able to decode HE AAC or not. If it can't do this, a 230 kbps/6ch AAC LC transcoding from 448 kbps/6ch AC-3 will certainly sound better on that player than a 230 kbps/6ch HE AAC file with a cutoff at ~8.5 kHz (without SBR).

Also, when transcoding from a 5.1 DTS source to 5.1 AAC, is it possible to equal or surpass the quality of an original 5.1 AC3?
Another theoretical question that no one has tested in practical listening tests yet, but it may be possible, because DTS is said to sound better than AC-3, and AAC LC has been proven to sound better in formal MPEG comparisons. On the other hand DTS -gt; AAC would mean transcoding with the usual drawbacks while producing an original AC-3 track is done from the studio digital master track, not from a lossy encoding.

I'm asking these questions because I'm about to back up a DVD that has both DTS and AC3 tracks and want to use the least possible audio bitrate so that I can make an anamorphic encode but would like as much audio quality as possible.
If you manage to encode the DTS multichannel track to AAC LC, I would recommend that method, but keeping the original AC-3 track (i.e. not transcoding it) might also be an option if it's not too big.

Well, the file will be played on a PC for now and maybe a modded XBOX with XMC in the future, so choosing HE-AAC wouldn't be a problem. I was going to use LC @ ~192kbps/6ch, but after reading this thread and a couple of others I think going for LC @ ~256kbps/6ch will be worth for the increased quality. My hearing is pretty crappy, so knowing that a DTS--gt;AAC transcoding could theoretically be of similar quality than the original AC3 (which is a 488kbps track in this case) is good enough. I could just use the AC3 track, but in that case I don't think I could go for anamorphic encoding and get decent results.
Thanks a lot for the thorough answer, it was very helpful .

Excuse me for beeing such a noob, but if I wan't to encode to 6ch lc-aac
1)What bitrate? Is 230 a good bitrate for a normal movie?
2)Which encoder? Should I use Nero or AACmachine?
3)Is there a preset (like --alt-preset standard in Lame) that I should use?

I've tried to search, but some of the threads are rather confusing. I think someone should write a guide about multichannel aac, as it seems to be a rather complex subject.

Originally posted by Chainmax
Well, the file will be played on a PC for now and maybe a modded XBOX with XMC in the future, so choosing HE-AAC wouldn't be a problem. I was going to use LC @ ~192kbps/6ch, but after reading this thread and a couple of others I think going for LC @ ~256kbps/6ch will be worth for the increased quality.
That's for sure, like I wrote in the FAAC related thread: going below 200 kbps/6ch with an AAC LC codec (be it FAAC, Nero or others) is the lower limit for this profile, but ~230 kbps/6ch using -q 75 already sounded very good to me with the LOTR II trailer. You may want to compare it to a ~190 kbps/6ch or lower HE AAC file, too, if you need the extra free space for a slightly better video encoding.

Thanks a lot for the thorough answer, it was very helpful .
You're welcome.

@Sir Integral Hellsing (what a name...): it only gets complicated if you have to use Nero (HE) AAC...  And don't use AACmachine, it uses the deprecated and buggy (for multichannel purposes) PsyTEL codec.

Originally posted by hans-jürgen
If you are aiming at this overall bitrate range for your AC-3 transcodings, you should rather use AAC LC (Low Complexity), not HE-AAC, because it needs much less CPU resources for multichannel playback (and also encoding). The sound will be similar or maybe even a little bit better, too (without SBR artifacts), because HE-AAC is rather meant to be used for even lower bitrates, i.e. below 200 kbps/6ch. You can find some recommendations for suitable FAAC encoder settings here.

What kind of preset do you recommend when using Nero Digital Audio Encoding? My first .Mp4 (6c/SBR) file-size was 369 mb. Original AC3-track=714 MB. Should I use CBR or VBR?

@Gircobain

Xvid settings: 1 b-frame (others settings default), MS6, GMC, VHQ4, Chroma motion, Trellis, Quants at default, no turbo and CQM=Didees sixofnine (Bitrate 3028). I am going to redo my encode, but this time without GMC and maybe even B-VOPS completely disabled. Disabling GMC and B-frames should probably reduce CPU-usage and make audio playback less stuttering (there's nothing more bothering than to listen at desynced audio, isn't it?)

Greetings,
Splashdriver

Still you didn't tell what are you using to decode XviD and if any post processing is applied

I'd advise you to try ffdshow with no post processing since your video bitrate is so high

Also I believe overlay mixer is the fastest video renderer so make sure it is selected in MPC

Yeah, I know my nick is kinda silly, but I couldn't come up with anything better...

I tried that guide on everwicked that you linked to in the quot;Important information for faac usersquot;-thread:
content/Xv...content-07.php
But foobar refuses to even open a ac3 file. I used normal installation. I couldn't find a plugin for ac3 either. What am I doing wrong? I'm using foobar2000 v0.8.2

Originally posted by gircobain
Still you didn't tell what are you using to decode XviD and if any post processing is applied

I'd advise you to try ffdshow with no post processing since your video bitrate is so high

Also I believe overlay mixer is the fastest video renderer so make sure it is selected in MPC

Ah yes....let's see, I'm using ffdshow to decode Xvid for quite a while. Post processing is disabled and overlay mixer was selected in MPC. Maybe it's the specs of the Xvid file+AAC(6c/SBR) which is causing jerkiness while playing. Edit: see Xvid settings above

@all
Does anyone knows what kinda preset to choose in Nero Digital? Hope to do this right this time, because encoding with Oagmachine takes very long on my machine.

Greetings,
Splashdriver

Originally posted by Sir Integral Hellsing
Excuse me for beeing such a noob, but if I wan't to encode to 6ch lc-aac
1)What bitrate? Is 230 a good bitrate for a normal movie?

as hans-jürgen said, the best would be if you test the quality for yourself, but i think ~230kbps for multichannel should be ok, maybe even less

2)Which encoder? Should I use Nero or AACmachine?

for stereo both provide nice quality, but for multichannel you shouldnt use aacmachine (which uses the psytel encoder internally), as its buggy with 5.1 (wrong channel mapping)
of course you can also try faac (an opensource aac encoder) for multichannel encoding

[/QUOTE]3)Is there a preset (like --alt-preset standard in Lame) that I should use?[/QUOTE]it depends on the encoder you want to use, but most aac encoder offer simply settings by default anyways

I've tried to search, but some of the threads are rather confusing. I think someone should write a guide about multichannel aac, as it seems to be a rather complex subject.

why should it be complex?

Complex maybe isn't the right word, english isn't my native language so I may express myself a bit odd sometimes. What I mean is that there are many factors, like he- or lc-aac, wich of them should I use for what bitrates, wich encoder etc. Some encoders seems to be buggy. But, maybe I'm just dumb and it's crystal clear to the rest of you. I'm a noob, I admit that, but getting started with xvid was much easier, lots of guides etc.

Thanks for the tip on faac, I'll try it.

But foobar refuses to even open a ac3 file. I used normal installation. I couldn't find a plugin for ac3 either. What am I doing wrong? I'm using foobar2000 v0.8.2

The ac3 plugin is included in the special installation download.html or you can find it here projects/kode54/index.php

Originally posted by Splashdriver
What kind of preset do you recommend when using Nero Digital Audio Encoding? My first .Mp4 (6c/SBR) file-size was 369 mb. Original AC3-track=714 MB. Should I use CBR or VBR?
Well, if decoding complexity is the problem on your PC (maybe it's also the overhead of the MKV container compared to MP4), don't use HE AAC, use AAC LC, either with Nero or FAAC. Then it doesn't matter much which codec you use, with Nero choose a VBR setting that results in ~85 kbps/stereo = 230 kbps/6ch. Keep in mind though that their bitrate estimation is rather unprecise and uses more kbps than announced most of the time.

With FAAC simply use quot;-q 75quot; (plus quot;-o output.mp4quot; if you want a MP4 file) on the command line or with e.g. foobar2000 and its foo_faac.dll GUI which means a VBR Quality of 75% resulting in the bitrates described above.

Originally posted by Sir Integral Hellsing
I tried that guide on everwicked that you linked to in the quot;Important information for faac usersquot;-thread:
content/Xv...content-07.php
But foobar refuses to even open a ac3 file. I used normal installation. I couldn't find a plugin for ac3 either. What am I doing wrong? I'm using foobar2000 v0.8.2
Like bobsc already wrote you need the special installer of foobar2000 and choose a custom installation with the AC-3 format enabled. You can check if foo_ac3.dll and foo_faac.dll are in the components folder afterwards.

And don't forget that the Everwicked guide is a little outdated in the meantime, e.g. the screenshot showing the usage of the Main profile in FAAC is plain wrong (LC would correct), and the recommended setting for video tracks is VBR Quality at 75%.

I finally managed to sucessfully encode a 6ch lc-aac file! At least I think I did (I can not say for sure as my 5.1 system isn't hooked up to my computer. When I play the file in foobar it reads quot;AAC 232 kbps 48000 hz 6 channelsquot;. I encoded using q=75 with faac through foobar.
Anyway, thanks to all of you for your help, if it weren't for you, I would still be stuck.

Originally posted by Sir Integral Hellsing
I finally managed to sucessfully encode a 6ch lc-aac file! At least I think I did (I can not say for sure as my 5.1 system isn't hooked up to my computer. When I play the file in foobar it reads quot;AAC 232 kbps 48000 hz 6 channelsquot;. I encoded using q=75 with faac through foobar.
Normally foobar2000 doesn't lie... except for the sample rate of AAC LC files equal to or lower than 24 kHz.  By the way, foobar also has a DSP module for downmixing 5.1 to stereo, so you can at least listen to the file with your normal speaker setup. This downmixer can also be used while encoding if you don't need or want 5.1 transcodings.