Mkv vs MP4 and aac 5.1 bitrate

[daWsOn_s]

Hello I have two questions.

I've always used mkv as container for avc video and aac audio. I made some searches and it seems that the majority of AVC players currently only supports mp4 as container...for example xbox 360 (what about PS3?)
So what's the difference? I mean they are only containers why some players should just boycott one? Do you think it's better for now to use mp4 for more support?

Second question. I have one AC3 5.1 track @ 448kbit, and I would like to reduce it to AAC. I can't recognize the difference between an original uncompressed track and the same compressed aac 128kbit stereo one ( 64 x 2 ), so if I want to keep the same bitrate quality with a multichannel track in aac 5.1 I should use 384kbit that means 64kbit x 6? Is that correct?
Why the aac profiles "advice" to use only up to 256kbit multichannel? Maybe the compression in 5.1 is different that I can use lower bitrate compared to stereo?

Thanks :D

[Sagekilla]

Hello I have two questions.

I've always used mkv as container for avc video and aac audio. I made some searches and it seems that the majority of AVC players currently only supports mp4 as container...for example xbox 360 (what about PS3?)
So what's the difference? I mean they are only containers why some players should just boycott one? Do you think it's better for now to use mp4 for more support?

Second question. I have one AC3 5.1 track @ 448kbit, and I would like to reduce it to AAC. I can't recognize the difference between an original uncompressed track and the same compressed aac 128kbit stereo one ( 64 x 2 ), so if I want to keep the same bitrate quality with a multichannel track in aac 5.1 I should use 384kbit that means 64kbit x 6? Is that correct?
Why the aac profiles "advice" to use only up to 256kbit multichannel? Maybe the compression in 5.1 is different that I can use lower bitrate compared to stereo?

Thanks :D

mp4 is the container set by the MPEG-4 standard, and mkv is an open source container. I can't explain it fully to you, but most (if not all) support in the industry right now is going towards supporting the MPEG-4/H.264 standard which means AVC in mp4, not mkv.

[daWsOn_s]

I guess this is a bad thing...mkv supports more audio formats and it's open!. I hope that mkv will be included someday in all players.

Hope somebody will answer to my audio question :)

[Sagekilla]

I guess this is a bad thing...mkv supports more audio formats and it's open!. I hope that mkv will be included someday in all players.

Hope somebody will answer to my audio question :)

I can somewhat answer your audio question too.. In the case of multichannel vs stereo audio, you can typically encode 5.1 AAC at a slightly lower bitrate than you would expect for similar quality to a stereo setup.

So, if stereo AAC sounds good to you at 128 kbps (64 kbps per channel,) it might be only 256 kbps necessary for 5.1 because of exploitations of channel similarities. IIRC, that was one of the (many) reasons why AAC could compress better. It's something similar to joint stereo I think.. If you don't know what Joint Stereo is, it's basically where the encoder creates a mid channel that has all the similarities between the two and subtracts that from the original audio to create a side channel that'll recreate the original stereo file at much higher quality possible.

I don't know if that's exactly how it works, but that's a general idea of how it works so you have an idea why AAC can compress 6 channel audio well at 256 kbps.

[daWsOn_s]

OK,
maybe it will be useful some method to understand how much bitrate every channel takes. For what I know for example 384kbit it's not divided perfectly 64kbit per 6 channels.

I tried to encode with megui at 384kbit CBR but the final file is 18MB bigger winamp says that the real bitrate is 414kbit...:scared: