infocalypse1
01-29-2009, 06:18
In a previous post I had mentioned that the O2 can record DMB and DAB broadcasts and stores the files with a .mtv file extension. This file format was unrecognized by any of the video players available to me, including VLC media player. Therefore, I set out to see what was up. Testing a sample file with gSpot gave little information other than that the file was an MPEG2 transport stream. A little research on T-DMB revealed that the transport stream used H.264 video format and one or more versions of aac for audio. A bit more research led me to the BIT Everest project (http://biteverest.googlepages.com/), an open source project focused on creating tools for DTV developers. One of the demo tools available was a utility for demuxing T-DMB transport streams!. I tried it on a sample .mtv file and, voila, it generated a h.264 video stream, and an audio stream. The video stream was readily playable via VLC player and other .264 tools. However, the audio file still isn't playable or readable by anything other than the O2 itself (both demuxed streams are readily accepted and read by the O2). I then went back to researching Korean T-DMB standards and found that the implementation uses an audio codec Bit Slice Arithmetic Coding (BSAC) which is a variant on .aac and is an ISO standard format with a file extension of .bsac. Thus far I have not found a usable windows-based codec for bsac, but am still looking. It is ironic that after doing all of this detective work, a quick look at the English O2 manual shows file support for .mtv, H.264, .aac, and bsac formats. I could have saved a bunch of time by simply researching the two "unknown" formats listed.
So what does this mean to non-Korean O2 users? First, implementation of T-DMB in Europe is likely to use standard .aac as the audio format rather than bsac. This should make demuxing of transport streams and remuxing into a more standard mp4 program stream pretty easy. Second, it is likely that O2 users in other asian countries can also expect to see similar variants to the Korean standard (looks like China's DMB standard will also use bsac for audio). Third, since the non-DMB enabled O2s still support the DMB file formats, anything recorded from DMB will still play on a non-DMB player. This may be useful to users of other Cowon models, especially the D2, which also is available w/ DMB in Korea. I'm finished on this topic, now that I know what's going on. However, I wanted to pass on my findings to other O2 users who may want to do editing of their recordings (e.g., take out commercials, etc.).
So what does this mean to non-Korean O2 users? First, implementation of T-DMB in Europe is likely to use standard .aac as the audio format rather than bsac. This should make demuxing of transport streams and remuxing into a more standard mp4 program stream pretty easy. Second, it is likely that O2 users in other asian countries can also expect to see similar variants to the Korean standard (looks like China's DMB standard will also use bsac for audio). Third, since the non-DMB enabled O2s still support the DMB file formats, anything recorded from DMB will still play on a non-DMB player. This may be useful to users of other Cowon models, especially the D2, which also is available w/ DMB in Korea. I'm finished on this topic, now that I know what's going on. However, I wanted to pass on my findings to other O2 users who may want to do editing of their recordings (e.g., take out commercials, etc.).