"Bit Rate" (VBR/CBR) flag in IFO

[yup_]

According to the "Video Attributes" table at http://www.mpucoder.com/DVD/ifo.html#vidatt bit 5 of byte 1 of this structure is a "VBR/CBR" flag, and such well-known programs as IFOEdit, PgcEdit, DVDRemake, VobBlanker allow to examine/edit it.

Recently I discovered that some DVD players incorrectly handle coordinates in menus if this flag is set to "CBR"("1").

After some investigation I found DVD-related patents that also contain description of this structure (VTSM_V_ATR / VTS_V_ATR). According to them the "VBR/CBR" flag does not exist at all, and bit 5 is a third (MSB) bit of the "Resolution" (frame size) field and must always be "0".
Also Philips DVD-Video Verifier reports next errors (for "PAL 720x576 CBR" flags for menu/title video streams):
********************************************************************
>>> [DVD] ERROR 4226 (ref. DVD-3 4.2.1 / BP 256 or 512) :
VTS(M)_V_ATR: Source_picture_resolution for PAL has the reserved value 4 for VTSI at byte 257 bit 2

>>> [DVD] ERROR 4226 (ref. DVD-3 4.2.1 / BP 256 or 512) :
VTS(M)_V_ATR: Source_picture_resolution for PAL has the reserved value 4 for VTSI at byte 513 bit 2
********************************************************************
(Binary representation of 4 (100b) agrees with patents about 3-bit-wide "Resolution" field.)

Can someone comment this?

[mpucoder]

I don't recall now where the description of that bit came from, but obviously it was never verified and is incorrect. Do these patents mention any meaning to values 4 through 7?

[r0lZ]

OK, I've removed the CBR/VBR info from PgcEdit. Luckily, it was not possible to edit that field with PgcEdit.

Thanks for the information, yup_!

[Ghitulescu]

Quoting EP737009


In the video attribute (VMGM_V_ATR), as shown in FIG. 8, bit number b8 to bit number b15 are allocated to the compression mode, frame rate, display aspect ratio, and display mode, which are the video attribute of the video object set 76 for the video manager menu (VMGM) and bit number b0 to bit number b7 are left empty for reservation for later use.
When "00" is written in bit numbers b15, b14, this means the menu video data has been compressed in the video compression mode on the basis of the MPEG-1 standard; and when "01" is written in bit numbers b15, b14, this means the menu video data has been compressed in the video compression mode on the basis of the MPEG-2 standard.
The other numbers are for reservation for later use. When "00" is written in bit numbers b13, b12, this means that the menu video data has a frame rate of 29.27/S at which 29.27 frames are reproduced every second.
Specifically, when "00" is written in bit numbers b13, b12, this means that the menu video data is TV-system video data according to the NTSC scheme and has a frame rate at which a single frame is drawn at a horizontal frequency of 60 Hz using 525 scanning lines. When "01" is written in bit numbers b13, b12, this means that the menu video data has a frame rate of 25/S at which 25 frames are reproduced every second.
Specifically, this means that the menu video data is TV-system video data according to the PAL scheme and has a frame rate at which a single frame is drawn at a frequency of 50 Hz using 625 scanning lines.
The other numerals in bit numbers b13, b12 are for reservation for later use.
Furthermore, when "00" is written in bit numbers b11, b10, this means that the menu video data has a display aspect ratio (ratio of height to width) of 3/4; and when "11" is written in bit numbers b11, b10, this means that the menu video data has a display aspect ratio (ratio of height to width) of 9/16. The other numbers are for reservation for later use.
Furthermore, when the display aspect ratio is 3/4, that is, when "00" is written in bit numbers b11, b10, "11" is written in bit numbers b9, b8.
When the display aspect ratio is 9/16, that is, when "11" is written in bit numbers b11, b10, whether the displaying of the menu video data in pan scan and/or letter box is permitted is written.
Specifically, when "00" is written in bit numbers b9, b8, this means that the displaying in either of pan scan and letter box is permitted; when "01" is written in bit numbers b9, b8, this means that the displaying in pan scan is permitted, but the displaying in letter box is inhibited; and when "10" is written in bit numbers b9, b8, this means that the displaying in pan scan is inhibited, but the displaying in letter box is permitted.
When "11" is written in bit numbers b9, b8, this means that the displaying is not particularly specified.
http://oi55.tinypic.com/kbup2s.jpg
I think the OCR had problems, the frame rate is 29.97 and not 29.27. I haven't changed it however.

[yup_]

Do these patents mention any meaning to values 4 through 7?
In all documents they are explicitly denoted as reserved.
For example: EP0869496B1, US 6167192 and US 6473561 "DVD disc, device and method for reproducing the same":
b5-3 of the source picture resolution is given as in the following table 13.
[Table 13]
b5-b3 source picture resolution
000 : 720*480 (525/60 system), 720*576 (625/50 system)
001 : 704*480 (525/60 system), 704*576 (625/50 system)
010 : 352*480 (525/60 system), 352*576 (625/50 system)
011 : 252*240 (525/60 system), 352*288 (625/50 system)
others : reserved

(And in patents related to HD video where the same VTS(M)_V_ATTR structure is present values 4-7 are used for higher resolutions.)

[mpucoder]

Thanks for the information, I've changed the table to reflect this. I waded through a lot of patents when I wrote that and discovered a lot of conflicting or just plain wrong information, so it took some testing and guessing (at a few). As both of you just showed, either OCR or humans distort the data (a non-standard frame rate, and "252x240" as the half-D1 resolution, which should be "352x240")
All these reserved bits show that there was some forward thinking in the design of the spec.

[Ghitulescu]

Glad to help.

[yup_]

(a non-standard frame rate, and "252x240" as the half-D1 resolution, which should be "352x240")

In fact, "252x4240" in all three documents!
I corrected the second number when was typing. :)