Movie Bitrate

[Penecho]

Hi, a little question:

When i got this:

Overall Bitrate : 3.629/2.903Kbs

Which Bitrate is the one of the Movie?? the 1st or the 2nd ?? and is the other one from the Menu??



Cu

[Susana]

That referes to how dvdrebuilder manages ntsc film/video content.

3.629/2.903 = 29.97/23.976 = 1.25

DVD frame rate is 29.97. In film content, 3:2 pulldown flags are inserted into mpeg-2 stream to repeat fields, so real frames are encoded at 2.903 kbps (@23.976), but "displayed" stream has a bitrate of 3.629 kbps (@29.97). In video content, there are no repeted fields, so "encoded" & "displayed" bitrate are the same, 3.629 kbps (@29.97).

[Incognitoid]

huh that makes sense now that I go back and do the calculations on my past logs. wish I had known this earlier, I thought the first number was the overall and the second number was the video bitrate but of course the numbers never worked out when you tried to add the audio bitrate to what I thought was the video bitrate.

So a follow up question then is that if these are bitrates for 29.97/23fps is this for the overall (audio + video), or just overall in the sense that it is only the overall for just video of all the video title sets. Hope that made sense.

also, although I've encoded many ntsc video movies, the two bitrates are almost always different, is this just a result of how rebuilder encodes everything at 23fps or whatever, then adds the flags later?

[jdobbs]

Yes. All NTSC discs are encoded at a common denominator of 23.976 so hybrid streams can be supported. As Susana said, the first number is the playback bitrate and the second number is the one that is passed to the encoder.

The "true playback" bitrate is the first number. That's the one that most other packages would report (in order to make themselves look better). I just like to be honest in the reporting. If a segment is encoded at 29.97 the first number represents both the playback bitrate and the "as stored" bitrate. If the stream is FILM, the first number is the "playback bitrate" and the second number is the "as it is stored" bitrate. The reason they are different is because in FILM mode the PULLDOWN flag tells the player to create an additional frame (during playback) for every four that are stored (23.976 -> 29.97)... thus the 25% difference.

[Incognitoid]

cool, cool. thanks for the response.