Log in

View Full Version : total bitrate and max video bitrate

XMEN3
17th July 2005, 18:50
Using dvd-rb the maximum bitrate for video is calculated as follows :
10.800 less the bitrate of the only subpicture stream used and less only the only audio stream used (the most significant from the list, I mean if there's 2 audio streams 448kbps and 192 the max bitrate for audio will be 448k)
Why selecting more audio streams the video bitrate is reduced proportionally as many streams i take?

sorry my english
jdobbs
18th July 2005, 12:27
The maximum bitrate allowable for video is 9800 -- so it can't go above that. While the combination of video/audio/subpictures can be 10.08Mbs, DVD-RB estimates maximum bitrate conservatively... so it starts at 9800.
XMEN3
18th July 2005, 16:02
no when i select audio with 448 the bitrate for video is set to 9350 (like that)...
Selecting one more audio track it goes to 8980 (like that)...
why?
The audio track is used once, i can't use 2 audio tracks once....
So the bitrate to romove for audio space is the most significant only.
If the PLAYER is reading the entire vob for decompression...i'm wrong...
Audio is not extracted on the fly from players?
Trahald
18th July 2005, 16:49
Its sorta hard to understand what you are trying to say.. but basically, the way dvd works.. the player has to read (well.. not HAS to but thats part of how the spec was based on) the whole stream, even audios that arent currently playing. so if you have video and 3 audios and no subs. then the max bitrate the video could be is 10.08 - audio1 bitrate - audio2 bitrate - audio3 bitrate. conservatively 9800 is better to use as encoders sometimes go over (spikes are ok if they are short enough.)
XMEN3
18th July 2005, 17:00
so 9800 is the total with all audios and subs? not the currently one used?
Trahald
18th July 2005, 17:16
uhmm.. 9800 is the total with video + all audios + all subs... meaning to get the video bitrate it is 9800 - all audios - subs. (subs use little so im not sure how much dvdrb removes for them if any)

so say if a vts has 768 dts 448 ac3 and 192 ac3 directors comments and no subs.. if you keep them all the calculation would be 9800 - 768 - 448 - 192 == 8392 as the max video bitrate..