CCE Encoding trick for SVCD to give more bits

[VidGuy]

I'm one of those guys who doesn't like cutting the credits. However, credits certainly don't need the bitrate of the rest of the movie. Here's my sleazy method:

1) Use your favorite bitrate calculator to determine the bitrate of the whole movie. Let's say we have 24000 frames @ 24 fps = 1000 second movie at a bitrate of 1800.

2) Use CCE and it's frame viewer to determine the frame number of the start of the end credits. Let's say they start at frame 20500.

3) Calculate saved bits for credits @ 500 avg =
(1800 - 500) * 3500 = 4550000. (3500 = 24000-20500)

4) Determine new bitrate for rest of movie =
Old bitrate + (saved bits / frames) =
1800 + (4550000 / 20500) = 1800 + 222 = 2022.

5) Encode first part at new bitrate (frames 0-20500)

6) Encode 2nd part at 500 (frames 20501-24000)

7) Join them with TMPGEnc (make sure you use the "Correct" button before doing the join).

8) If I recall correctly TMPGEnc gives you an mpg file instead of an mpv file after the join - use the demultiplexer to demultiplex the mpg file.

9) Use BBMPeg to join the original audio with the new video.

This method seems to be frame accurate, but in the end, it doesn't matter much since a couple of frames out of synch on the sound won't be noticed since it's just rolling credits.

P.S. I've found that this method can be used "after the fact" if you use MPeg2VCR to cut the credits off of the original, then use TMPGEnc to demux the output of MPeg2VCR, then use TMPGEnc to join "new credits" to the original.


<font size=-1>[ This Message was edited by: VidGuy on 2001-10-01 10:15:48 ]</font>

<font size=-1>[ This Message was edited by: VidGuy on 2001-10-01 10:17:06 ]</font>

<font size=-1>[ This Message was edited by: VidGuy on 2001-10-01 10:17:59 ]</font>

[adam]

I don't understand why anyone would do this extra work. The encoder does exactly what your method does already. If your encoding in vbr than the credits will already be encoded in a very low bitrate. Even with a very high average bitrate and very high quality settings the encoder will still probably never use much more than 500kbits for the credits.

The only time I could see this being viable was if you were encoding in cbr, but then you'd be wasting so much space anyway that what little bitrate you save on the credits would be negligable.

[VidGuy]

That's what I originally thought. However, if you use CCE and use the advanced setting - I found to my horror that the credits are in fact recorded at a very HIGH bitrate (higher than the average that was set), presumably because of the sharp edge of the characters. For example, I had an 1800 Avg, 2400 Max video, and the average on the rolling credits was 1900-2000......

I can assure you, it saved me MANY megabytes off of the final picture.

<font size=-1>[ This Message was edited by: VidGuy on 2001-10-01 16:13:00 ]</font>

[adam]

Hmm, Ill have to take a look at the bitrate levels in some of my svcds, I never noticed that. If its true it must be a bug because any encoder should use significantly less bitrate on credit scenes.

Anyway there is a MUCH easier way to do what you suggest, CCE has a function specifically for it. Do your first pass to generate your .vaf file. Load this and go into the advanced settings. From here you can manually adjust how much bitrate goes to each scene, while allowing cce to determine the bitrate levels for all the rest. Just go to the end and drop the bitrate level way down. So now theres no need to do multiple encodes or to join.

Also just for other peoples info I don't feel this procedure is needed with TMPGenc. Ive checked numerous encoding logs and credits always seem to use minimal bitrate when encoded in vbr.