In article , Don Pearce
wrote:

[big snip]

Interesting. Presumably the player just ignores the first data chunks
until it finds a frame header, then uses the info from that to read the
succeeding stuff.

I will be doing some more checking later today if I get a chance. But IIUC
I am editing by snipping at chunk (frame) boundaries. That is certainly
what I am trying to get my edit program to do. If so, here will be a frame
header at the start of each output file because it was present at the
relevant point in the source file.

I do have a (three, actually) general editor(s) that display hex. So will
check that way. Can also then scan for hex patterns (sequences) to find
where header declarations repeat. May also write a simple util for this.

Thanks for giving me the URL for the info on the mpeg file format. It means
I can modify my track editor to read the file and determine the frame size
and data rate. At present I have to tell it the value in kbps to get the
times and durations of the snipped files correct.

Is there a similar spec for ac3 (Dolby)? I'm also looking at files of that
type. I can export the ac3 stream from home-recorded video VOB files and
then play these on my computer. Can also edit them, but again I have
currently to tell my track editor what bitrate to presume as I don't know
how to read this from the actual ac3 data.

At some point I'd also like to be able to transcode ac3 to mp3 - ideally
with no 'losses' if that is possible. At present I'd have to convert via
using LPCM as an intermediate. That is fine, but slower and probably gives
more scope for losses - although I suppose I could use 32bit LPCM to
minimise this. :-)

FWIW I'm currently writing a series of articles and utility applications
for a RO computer mag - and for my own use. This in turn is useful as a
basis for finding out things that might then pop up in HFN. So am finding
this very interesting.

Slainte,

Jim

--
Change 'noise' to 'jcgl' if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html