[VCDImager Bugs/Devel] Re: MPEG-2/ stuff...

[Jorgensen, Jens]

Herbert Valerio Riedel wrote:

> hey!
>
> (please cc: your answer to bug-vcdimager if it contains new
> information :)
>
> I was just wondering about the file structure...
>
> what's the exact naming of the directory and files within, where those
> 'avseq..' file are in?

MPEG2
   AVSEQ01.MPG
   AVSEQ02.MPG
   [...]

where AVSEQ01.MPG is track 2, AVSEQ02.MPG is track 3, etc.

> and what exactly should those fileentries point to,
> the beginning of the actual mpeg stream, or the beginning of the cd track
> containing that mpeg stream?

Well, the first sector of the file should be the first sector of the 
corresponding track and the last sector of the file should be the last sector 
of the corresponding track. That's all it says. Does that make sense?

> what file length should one set in the ISO
> fs?

I guess you just take the total number of sectors * 2324? It doesn't say 
anything about this explicitly that I can see.

> and what about the padding of the mpeg stream? how many padding zero
> blocks have to be inserted before/after the stream?

The track has to start with a Pause encoding of minimum 150 Empty sectors. (See 
below for "Empty sector" definition.

> is there some
> alignment thingie to care about?

Nope, not that I can see.

> oh... just sprang to mind: for VCD2.0/1.x you have to detect the type of
> mpeg1 block (audio, video, program/other) and set that in form2 subheader,
> do I still have to do the same for mpeg2 & SVCD1.0?

The subheader is a four-byte field repeated. The first byte is file number, the 
second channel number, the third submode and the fourth coding information (I 
don't know if this is standard or not). There are three types of sectors for 
SuperVCD, Empty, Data, and MPEG.

Empy sector: file number = 0x0, channel number = 0x0, submode = 0x20, coding 
information = 0x0.

Data sector: file number = 0x0, channel number = 0x0, submode = 0x08 | 
eof_flag, coding information = 0x0.

MPEG sector: file number = 0x01, channel number = 0x01, submode = 0x62 | 
trigger_flag | eof_flag | eor_flag.

eof_flag is 0x80 for the last sector of any file or Play Item, 0x0 otherwise

trigger_flag is 0x10 for any sector where the device is supposed to execute the 
Auto_pause function, 0x0 otherwise

eor_flag is 0x01 for any sector where the sequence_end_code of a Still Picture 
has the End of Record bit set to 1, 0x0 otherwise

> ... we're getting close I think...

Yeah! Sorry it took me a while to get this response back to you.

--
Jens B. Jorgensen
address@hidden