6ch HE-AAC sounds "Metallic"

[Coren]

I've been trying to convert a movie to mkv with h264 video and dual he-aac audio, but there's this thing that's been bugging me.

I have a 2.0 he-aac and a 5.1 he-aac sound file, encoded with the Nero encoder through OagMachine. Both files play fine when I open them seperately.
However, when I mux the files together (I've tried MKV MUX and MKVtoolnix), the 5.1 file sounds very metallic, all of a sudden. As if the words were spoken by a robot on helium :p
The 2.0 file plays just fine, though.

I don't have a clue where this problem comes from.
Any ideas?

I use the latest ffdshow to play my files, and I've already tried CoreAAC, didn't help.

If you need more info, just ask.

Coren

[bond]

i assume you didnt set the flag which tells that the stream is he-aac and therefore the decoder decodes it without the sbr part -> crappy quality

[Coren]

Actually, I did.

I thought of that too, but I re-muxed the files and checked (and double checked) the flags. Same problem.

Coren

[Teegedeck]

Check which filters play back the files before and after remuxing. Are they the same?

[Coren]

Both files use the same filters, as far as I can see.

- AC3Filter (just for the mixing matrix, I suppose)
- ffdshow audio decoder (still active, for some reason, even though I disabled ffdshow's aac decoder)
- CoreAAC Decoder
- AAC Parser

One thing I've noticed is that in the mkv file, when I check the CoreAAC properties, the sampling rate is indicated as 22050 -> 44100, but when I play the AAC files seperately, it says 44100 -> 44100.

Also, the 2.0 file is set as the standard audio track, so when I open the movie, it plays fine. Then I switch to the 5.1 file, I get the metallic sound. When I switch back to the 2.0 file, though, the sound just plays twice as fast.

My guess is something's wrong with the sample rate. Any idea how to fix it?

Coren

[sillKotscha]

I found out that ffdshow_audio suits me best and I would do the following...
(presupposed you use S/PDIF)

- enable aac decoder (and any other decoder you like)
- click "volume" -> 'normalize' and max. amp. 500% should be preclick'd (no more low volume aac_audio ;) )
- enable mixer and set output speaker config to: "same as input" (your choice: unclick "expand stereo")
- set output to AC3 (leave bitrate or change it to 448)... maybe change merit of wave_out by choosing "connect to: WaveOut" and than back to "any filter"
- and at least you should do one last step... -> click 'resample': resample to: 48000khz, 'mode' choose: libavcodec_"what suits you best" and resample if samplerate is below 48000khz

I hope I didn't forget something and should be done.

Tell me if it worked ;)

EDIT: btw, "metallic" sounds like directsound is used... if you like your config and you won't use ffdshow as aac_decoder, than try wave_out

[Coren]

Well, setting the output to ac3 seems to have worked (can someone explain why? 16 bits works for the 2.0 stream, 32 bits for the 5.1 stream, but not the other way around), but then things started to get choppy. Resampling to 48000 solved this choppiness.

So yeah, the audio finally plays now. But I'm still kind of annoyed that I have to use ffdshow to decode aac. I'm getting some light artifacts I didn't get with CoreAAC. And my AC3Filter is gone from the filter list now, so I can't access the matrix. I can use ffdshow's matrix, but I liked the other one beter :p

Yeah, I know, I'm nitpicking. ^_^

Thanks for your help, I can finally get all my files to play now!

Coren

(note to whomever this might interest: since I've started using x264, XviD feels butt-ugly! The encoder still needs some improvements, but I'm really amazed at what it can do already)

[Backflip]

Nice, what are you using to encode to x264? GK? MEGUI?

[Coren]

Actually, I just use VirtualDub. >.>

Hadn't even heard of MEGUI before, I'll have to check it out.

Coren