#Mixing Audio and Data
6 messages in this thread
Is it possible to mix data and normal CD Audio on the same disc? I have a
client who wants to put the text of speeches and the speeches themselves on the
same CD. He wants to be able to access the text by putting the CD in a CDROM
drive. He wants to be able to play the speeches by putting the CD into a
normal CD Audio Player. Is this possible? Will each kind of drive / player be
able to tell what information on the disk is meant for it and should be
processed and what should be ignored?
A music CD can contain up to an hour of music on it right? Can you put more
data than that (eg 2, 4, or 6 hours) of recorded speech on a CD and still play
the speech on normal disc player? This doesn't seem possible to me but I told
my client that I'd research it for him.
Thanks in advance for your help.
– Eric
Eric,
Yes, mixed mode discs are possible, and have been done successfully for some
time. Generally, you need to tell the audio player which track to read, as if
you were choosing a specific song, since the tracks with the data would be
unintelligible to the audio player. The CDROM player should be able to discern
from the TOC where to look for data.
Compression of audio can be done in a CDROM environment, but for straight "Red
Book" audio it's impractical. Either you would need special decompression
hardware/firmware in the audio player (which doesn't exist as far as I know) or
there would have to be a computer interface to do software decompression to
play back the sound. What is possible is to use a lower sampling rate (speech
doesn't require the same bandwidth as music), which might save some disc space.
Please ask a digital audio specialist about that, though. It's not my field and
I'm just guessing.
Kathy Cochrane
[GO ONEOFF]
Eric,
Kathys' comments are very good guesses<g>. Several comments though.
(1). "Client wants to hear speeches on standard audio player". This limits you
to 74 minutes and 99 audio tracks
(2). If it was a computer accessed player. you can double this by only
recording each speech on a single channel.
(3). More compression than this requires specialized hardware. i.e. CD-I, Fully
implemented CD-XA, A Photo CD player, etc.
(4). A warning, Some (Most?) audio players don't recognize and skip digital
data tracks they try to play them!.
Glen
Glen,
Isn't that what I said? 😉 (Don't worry — I confused even myself on that
one.)
Kathy
[GO ONEOFF]
Yes, you can mix data and audio on the same CD-ROM. The data track comes first
and then the audio tracks. The audio tracks can be played on a standard CD
audio player, but the customer must skip the first track. Some audio players
will make some harsh sounds if the first track is played. The maximum play
time for an audio CD is about 74 minutes. Any data added to the CD will
subtract from that time. Six hours of audio could be put on a CD-ROM, but the
data would have to be stored in a method that would not be compatible with a CD
audio player. Nimbus Information systems has recently announced a device that
extends the recording capabilities of a CD. It requires a conversion box that
is attached to a compatible CD player (most CD audio players are claimed to be
compatible). This device also allows the playback of video. Adding additional
CD with the audio might be the best way to go. It wouldn't add that much to
the final cost of the product. In the future CD players with blue or green
lasers may increase CD capability.
Thanks for the info, Bruce.
– Eric