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Old 29th October 2001, 23:35   #1  |  Link
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Join Date: Oct 2001
Location: YU
Posts: 1
800 MB AVIs to 1 CD ?

Write 800 MB AVIs to a single 80 min CD ????

Here is my idea:

On an 80 min CD we can record 80 minutes of audio content or 700 MB of data content.

Now do some math!
Audio is 2 streams of 16 bit data with the sampling rate of 44100. So, in one second we have:
2 * 16 bits * 44100 1/s = 1411200 bits / second = 176400 bytes / second.
In 80 minutes of audio there is
80 * 60 * 176400 bytes = 846 720 000 bytes = 826875 kB = 807,5 MB

Clearly, for the CDFS we loose about 100 MB of space compared to the audio.

On a movie disk we have: the autolauncher files, various player / codec install files,
optionally some extra features (menus, pictures etc.), subtitle files and finally
the avi file(s).

The avi file is a largest file - the file. All the other files are small. So what we have to do
is find a way to absolutely precisely write to the disk the program files and others except
the big avi file (written like CDFS). This would take up to 10 MB of disk space.

The greatest (and hardest) now : write the avi file to disk as PCM audio.

Is it possible? Yes it is! How?

Well, there is a CD format called Mixed-Mode CD. This CD contains one ISO CD-ROM track with
data on it and the rest of the tracs is audio PCM tracs.

The problem is how to convert an AVI file to PCM. This is how:
We should have an audio wave editor application with the capability of opening PCM RAW format.
But first let's see the AVIs filesize: it have to be the multiple of 75 (don't ask me why -
this is how audio data is written to the disk 31 * 75 byte blocks = 2325 bytes / sector on CD).
So, the lenght of our avi file has to be enlarged to the next multiple of 75 (so max by 74 bytes)

Make a textfile with the apropriat size and join the tho files. Now the filesize is multiple of
75 and is still a valid AVI.

Now, in our wave editing application open the AVI as PCM RAW. When asked for format settings,
it is : channels:STEREO resolution:16 BIT samle rate:44100
The audio format on a CD is the same.

When the AVI is opened save it as a WAV file. Yes! You heard me good! As a WAV file.

This resulting WAV file will be burnt on our CD's audio track.

So, on the CD there will be the prog and other files on a CDFS track,
and the avi as a PCM audio track.

Technicly, the avi could be 800 MB in size and a few megs for other data; all fitting on
one 80 min CD.

We have to find a way to force our avi player (through a filter!?) to read this PCM audio track
and treat it as a valid AVI. The problem is that I don't now how to do it.
It should work like some audio grabbing utility which sees the track as a single PCM file.
All the AVI headers are on the beginning of the PCM data. When you grab this file to a PCM file

Data errors made during the recording and grabbing processes are so small, that it can't be
seen on the final playing AVI. - Multimedia files are resistant to some ammount of data errors,
or in other words - there wouldn't be any picture and sound corruption when there is just a few
bits of error. For fewer bits of error - use lower burning speeds!!!!!

There is a CDFS.VXD version allowing Windows to see the audio tracks on an audio CD as WAV files.

So it has to be modified to alow Windows to see the tracks as RAW PCM. Why?
You can't force Windows to treat a WAV file with WAV header as AVI video with a certain FOURCC.

The otherr thing is, it had to see the audio tracks as RAW PCM and the ISO DATA TRACK with
the launcher , player etc. files.

I don't know anything about coding Windows filters and virtual device drivers, but such a device
would allow us to play with MicroDVDPlayer an AVI file from a Mixed-Mode CD audio track (through
ASPI or WinNT/2k calls).

If someone can do something about this, or you have other ways to do this contact me please!!!

My e-mail adresse is : gamjuhas@ptt.yu; or juhiatti@freemail.hu .

Greetings from juhili (aka juhi).
juhiatti is offline   Reply With Quote

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