Most DVD recorders use a very limited file system when recording video,
and they artificially combine multiple MPEG bit streams into one continuous file.
Usually with a file name extension of ".VRO", ".REC", or ".VOB",
those DVD recorder files contain multiple video segments each of which
may use very different MPEG video and audio encoders.
A DVD recorder can read this file by the help of an additional index file
generated by itself; but those index files are mostly proprietary and
not known to an external software editor.
As a result, most MPEG editors will encounter great difficulty in loading
and editing those files, some of which may even crash.
If an MPEG editor can open those files successfully, rarely can it read
the content correctly. In those case, the common symptoms are
(a) the length of video is too short, much shorter than what its file size has indicated;
(b) the video and audio are completely out-of-sync; and
(c) no random seek can be performed correctly.
To resolve this problem, we have created a tool called MBS Scanner,
which scans and then disassembles a DVD recorder file into a set of segments.
When a single MPEG file contains one of the three changes listed below, we refer
it as a Multiple Bit Stream (MBS) MPEG file.
1. timebase change, such as a time code restart;
2. video encoder settings change, such as image size, frame rate,
and bit rate; and
3. audio encoder settings change, such as sampling frequency, bit
rate, and number of sound channels.
As defined in MPEG standards, an MPEG movie stream should have a continuous
time code to assist a decoder to synchronize its video and audio presentations.
Also, an MPEG movie stream should not change, in the middle of the stream, its
video encoder settings, or its audio encoder settings.
When an MPEG file contains one or all of the changes listed above, the editor
will not be able to handle it correctly.
Typical examples of such files are MPEG files created by a digital camcorder
with an internal MPEG recorder.
For a digital camcorder, one common usage is to take a sequence of shots and
stops. And between shots, the camera settings may be changed, such as switching
from an "SP" mode to an "LP" mode, which is essentially changing the video
resolution and bit rate. For some camcorder, it also restarts the time code
after a stop.
When a single MPEG file contains those changes within the file, we refer it
as a Multiple Bit Stream (MBS) MPEG file.
Since an MPEG editor cannot correctly decode the second or the following
segments of the same MPEG file without some additional information, and since
it's hard to design a flexible MPEG player that can dynamically switch MPEG
codec, the next best solution and perhaps the simplest solution to this problem
is to divide the file into multiple segments, and treat each segment as an
individual MPEG file, but without physically creating such segment files. This
is what this utility does.
By scanning the MPEG file for any restart of its timecode and any change of
MPEG encoder settings, it creates a list of segment files each of which saves a
starting file offset and an ending file offset.
The segment file can be recognized by the MPEG editor by its file name
extension of ".mbs", and be loaded properly as one complete MPEG stream.
Common examples of MBS files are VRO (".vro") files, DVD-R/W (".rec") files
created by a DVD-R/W video recorder, and even some standard DVD (".vob") files.
The following is an example of multi-segment MPEG file,
which contains two segments of MPEG recorded with a 720x480 resolution for the
first segment and a 352x480 resolution for the second segment.
Two ".mbs" files will be created by the scanning process, and listed below.
(1) D:\DVD recorder\PBC_ch9.vro_1.mbs
File= D:\DVD recorder\PBC_ch9.vro
Segment= 0 93235200
(2) D:\DVD recorder\PBC_ch9.vro_2.mbs
File= D:\DVD recorder\PBC_ch9.vro
Segment= 93235200 147796772
Please also read the sections on MBS file scan.
Combine Multiple Segment Files Into One Continuous Stream
Another usage of this MBS file format is to combine a set
of MPEG files which are really segments of one
continuous MPEG stream, but cut into small pieces
in order to satisfy the limitation of a file system, for example.
One typical example is the set of VOB files for one
DVD program, such as the following list.
The corresponding ".mbs" file for this example is the following.
This is the reverse of a multi-segment file as explained previously.
Again, the MPEG editor will load this ".mbs" file and
treat it as one continuous MPEG stream.
A different solution to the VOB file example given above
is to use the newly created DVD Reader,
which also heavily dependent on the usage of the MBS file format.
How to Convert Your MPEG Movies for iPod and PSP?
How to Edit Out Commercials?
How to build a DVD with multiple titles and an introductory video?
How to load DVD video file (VIDEO_TS) and use the DVD Reader?
Other FAQ (Frequently Asked Questions)