HE-ACC 5.1 to AC3 questions

[trooper11]

Ive been trying to convert some HE-ACC 5.1 audio to 5.1 AC3. I have a set of mkv files and i extracted two audio streams from it, one is 5.1 HE-ACC (180.1 kbps), the other is 2 channel HE-ACC (61.4kbps).

when i extract them, the 5.1 audio is ~31mb while the 2 channel is ~11mb. these tracks are about 25 minutes long.


now that seems normal, but then when i go to graphedit to convert these to ac3, the resulting files are all the same size, 38.778 mb, right down to the last kb. Wether is 5.1 or 2, its the same resulting ac3 file size.

this cant be right, so where could i be going wrong in the conversion? when i listen to each track on my 5.1 system, the 5.1 track does sound more properly spaced over the channels and the overall volume is lower, while the 2 channel is louder and not well placed over the speakers.

i would think that a 5.1 track in ac3 would be alot larger then 38mb, but its just strange that every track i have done is the same size.

[trooper11]

ok i did make a mistake and was converting the same 5.1 and 2 channel tracks over and over, i didnt extra different audio from each episodes.

but evne after fixing that and redoing them, each ep resulting ac3 file is the same size wether its 5.1 or 2 channel. anyone have any suggestiong on how to fix this?

[stephanV]

File size depends on the bit rate you set, so if you use the same for both 5.1 and 2 ch then both will have the same. For DVDs its normal to have 448 kbps for 5.1 and 192 kbps for 2 ch AC3.

[trooper11]

oh i didnt realize that.

i chose a 224 bitrate for both tracks. i hope that doesnt degrade the 5.1 track

[stephanV]

it will