[Originally posted by jfaulkner on 2007-02-15 15:22:58-08]
I have a tool which works with mpg movies and im looking for resources regarding extracting the duration in particular, and any other information i can such as fps, bitrate, GOP table, etc., in general - directly from the mpg file. I noticed this thread discussing the support of mpg format in this regard, is there a resource available for how it was accomplished?
thanks in advance,
John Faulkner
[Originally posted by exiftool on 2007-02-15 17:01:12-08]
Hi John,
An MPG duration can be calculated approximately by taking the
file size (in bits) and dividing by the combined audio+video bitrate.
The accuracy of this calculation can be improved by adjusting the
result for MPEG overhead, but determining the constants to do this
is a bit of a black art as far as I can tell.
The only other way is to parse the entire bitstream to derive the
true bit length for the audio/video, but I don't do this in ExifTool
because it is too time consuming to scan the entire file.
- Phil