What does [0xc0] mean ??

[schrakapouet]

Hi there,

I'm just curious about something. When I analyze some files with Media info or Avicodec, I can read stuff, in the audio codec name part , like "mpeg1 layer 2(mp2)[0xc0]", or "mpeg1 layer 2(mp2)" and "mpeg1 layer 2[0xc0]". Those are the three different type of codec I met until now.
I'd like to know the difference between the three codecs.

What does [0xc0] mean?
What does (mp2) mean and what does it mean when it's missing ? Is that mp3 then?


Thanks !

[jman98]

There is no difference between the 3. They are all what is generally called MPEG audio (although technically it is MPEG-1, layer 2 audo).

Audio and video types have codes assigned to them. I don't know who decides what media gets which code. 0xc0 simply identifies the audio as being MPEG-1 layer 2 audio. Dolby AC3 has its own code, but I don't remember that one offhand.

MP2 is simply another name for MPEG-1, layer 2 audio. It can also mean MPEG-2 video, so generally using MP2 to refer to audio should be avoided unless you specifically state that you are referring to audio. It means nothing when it's missing as all 3 of those audio names you listed are the same thing. It's not MP3 either. MP3 is sort of a successor to MPEG-1, layer 2 audio. MEPG-1, layer 2 audio is actually a very high quality audio format, despite the erroneous belief that some people here in these forums have that it is crap. It is NOT crap. It actually can produce audio files truer to the original source file at bit rates over 224 Kbps than MP3 can. MP3 was not invented because MPEG-1, layer 2 audio sucked. MP3 was invented because MPEG-1, layer 2 worked fine, but it didn't compress enough. MP3 was invented specifically to produce reasonably high quality audio files at lower file sizes than MPEG-1, layer 2 with more emphasis being on the lower file sizes than quality of audio. MP3 became successful because the small file sizes it produced were very important in the 1990s when many people did not have home PCs and those who did had slow dial up connections to the internet. Also, the lack of DRM meant that MP3s could easily be shared, which also made it popular. Finally, the company that invented MP3 (Franhauffer or something like that) licensed their encoders at reasonable prices and their encoders got hacked and made available by hackers, which encouraged the spread of MP3. But MPEG-1, layer 2 audio is very good quality and like I said at higher bit rates it can actually produce superior files to MP3.

[Cornucopia]

This refers to the stream id# within the program/system mpeg container stream.

Most audio streams are 0xc# (starting with the 1st stream usually = 0), and video streams are 0x0# (also starting w/ 1st stream usu. = 0). Non-mpeg or non-standard streams would have other stream #s.
This is all similar to the PID in a Transport stream.

Scott

[schrakapouet]

thank you very much !!!! :P

[jman98]

Thanks for the correction, Scott. I thought that each type of audio always got the same code each time, but your explanation makes better sense and does explain some things I've seen.