Bits and bytes and VCD bitrate trivia

[SeeingMole]

I'm reading in the manual.txt from VCDImager.

In there I noticed this additional info about the VCD 2.0 spec:

-------------
By adding PAL support to the Video CD 1.1 specification, the following
resolutions became available:

* 352 x 240 @ 29.97 Hz (NTSC).

* 352 x 240 @ 23.976 Hz (FILM).

* 352 x 288 @ 25 Hz (PAL).

For segment play items the following audio encodings became
available:

* Joint stereo, stereo or dual channel audio streams at 128, 192, 224 or 384 kbit/sec bitrate.

* Mono audio streams at 64, 96 or 192 kbit/sec bitrate.

Also the possibility to have audio only streams and still
pictures(1) was provided. The bit-rate of multiplex-ed streams should be kept under 174300 bytes/sec in order to accommodate single speed drives.


------------


Now, is 1 kilo bit = 1024 or 1000 bits?


Because if I take 1150 + 224 x 1024 / 8 = 175872 (Over the mentioned limit)
But 1150 + 224 x 1000 / 8 = 171750 (within the limit)

So, 1 kilobits when it comes to VCD bitrate is 1000 bits?

According to this info, it should be possible to use for example audio bitrate of 128 and video of 1266 and still be 100% VCD 2.0 compliant. (1266 + 128 x 1000 / 8 = 174250)

VCD 1.1 is useless for me anyway because according to the same file, PAL resolutions isn't even a part of VCD 1.1 and was first introduced in VCD 2.0. All my VCDs are PAL.

What is your opinion about this?

[hvr]

try the calculation a bit differently;

taken from the vcd on cdi 4.1 manual...
<TABLE BORDER=0 ALIGN=CENTER WIDTH=85%><TR><TD><font size=-1>Quote:</font><HR size=1 color=black></TD></TR><TR><TD><FONT SIZE=-1><BLOCKQUOTE>APPENDIX C
Video encoding

Requirements/recommendations imposed by Video-CD Specification 2.0:

Picture size/ Picture rate

352 x 240 / 29.97 Hz
352 x 240 / 23.976 Hz
352 x 288 / 25 Hz

Bit rate:

Maximum 1151929.1 bits/sec
...</BLOCKQUOTE></FONT></TD></TR><TR><TD><HR size=1 color=black></TD></TR></TABLE>
so your 1150 'kbit' are to be considered 1000-sized k's

>>> (1151929.1 + (224 * 1024)) / 8
172663.1375

which is clearly under (but it's not wasted, see below!) 174300;

what you haven't considered in your calculation are the bits required for accommodating the program stream packetizing... (most notably pack header and pes headers)

btw, for sequence items you are restricted to 224 kbps stereo audio, it's only for segment items where whitebook constraints are relaxed...

[SeeingMole]

Just noticed the "segment" word.

What's that? Menus and stuff?

[vitualis]

Segment items are placed in the first physical track of a VCD and under the "segment" folder in the filesystem.

They are generally used for items used in menus, though not necessarily.

Regards.