MKVs: downmix ac3 6-channels to ac3 2-channels and remux

[kwanbis]

I have a WD TV, and somehow, MKVs with 6 channels ac3 do not play sound on my TV, but 2 channels ones ac3 do.

[b]UPDATE: I had my WD TV to DIGITAL AUDIO, instead than STEREO.

It looks like if the audio is 2 channels, the WD TV would do STEREO anyway, but for the 6 channels, it would try to do DIGITAL.

So i set it back to STEREO and all is playing perfectly.

But i'm still interested on knowing:

1) how can i specify FPS while doing the MKVmerge on the command line:
mkvmerge -o test.mkv video.h264 audio.ac3 sub.srt

2) if i already have an mkv, how do i add another file to it?

------------------------- OLD POST --------------------------------

So i'm trying to find out the quickets way of extracting the the ac3, downsampling it to 2 channels, and then remerging to the mkv.

I-m experimenting a little, since i-m really not much into video, unless i need to do something like now, so:

1) eac3to a.mkv
MKV, 1 video track, 1 audio track, 0:41:46, 24p /1.001
1: h264/AVC, English, 720p24 /1.001
2: AC3, 5.1 channels, 384kbps, 48khz, dialnorm: -27dB

2) eac3to a.mkv 1: video.h264 2: audio.ac3

3) eac3to audio.ac3 audio2.ac3 -down2

4) eac3to audio.ac3 audio2.wav

5) neroaacenc.exe -q 1 -if audio2.wav -of audio2.aac

So now i have:

video.h264 (original video)
audio.ac3 (this is the original 6 channels ac3)
audio2.ac3 (ac3 downsampled to 2 channels)
audio2.aac (aac downsampled to 2 channels)

I then tried:

mp4box -add "video.h264:fps=23.976" -add "audio2.aac:lang=en" "a-audio2-aac.mp4"

mp4box -add "video.h264:fps=23.976" -add "audio2.ac3:lang=en" "a-audio2-ac3.mp4"

mkvmerge -o a-audio2-aac.mkv video.h264 audio2.aac

mkvmerge -o a-audio2-ac3.mkv video.h264 audio2.ac3

I ended up with:

a-audio2-aac.mp4 plays perfectly.

a-audio2-ac3.mp4 no sound (is an mp4 restriction?)

a-audio2-ac3.mkv 1 sec delay

a-audio2-aac.mkv 1 sec delay

So, i was wondering, why the 1 sec delay (audio plays latter than the vide)? Is it because i-m not specifying the FPS? How do i do it?

And last, since i already have an MKV with audio and ac3, how can i add the 2 channel ac3?

Thanks.

[Baldrick]

Maybe avidemux or xvid4psp, under video choose copy under audio choose ac3 2 channels, save as a new mkv.

[kwanbis]

UPDATE: I had my WD TV to DIGITAL AUDIO, instead than STEREO.

It looks like if the audio is 2 channels, the WD TV would do STEREO anyway, but for the 6 channels, it would try to do DIGITAL.

So i set it back to STEREO and all is playing perfectly.

But i'm still interested on knowing:

1) how can i specify FPS while doing the MKVmerge on the command line:
mkvmerge -o test.mkv video.h264 audio.ac3 sub.srt

2) if i already have an mkv, how do i add another file to it?

[poisondeathray]

all the command line directions are listed in the documentation, for mkvmerge
http://www.bunkus.org/videotools/mkv.../mkvmerge.html

e.g. to specify 23.976 fps for track 0:

--default-duration 0:24000/1001fps

It's much much easier to use mkvmergegui. You can show the command line or copy to clipboard within the GUI, a great way to learn.

[kwanbis]

Excellent, thanks.