[Mp4-tech] (no subject)

[Wesley De Neve]

Dear Adam,
There are quite some tools out there for analyzing or manipulating MP4 files.
- MP4Creator from the MPEG4IP project (http://www.mpeg4ip.net/);
- MP4Box from the GPAC project (http://gpac.sourceforge.net/);
- Atomic Browser (http://www.atomicbrowser.com/);
- ...
Note that the 'mdat' box contains the actual media samples, and not the header information. The resolution of a video track can for instance be found in the 'tkhd' box/atom.
The following XML fragment is for example created by making use of the dump option of MP4Box (mp4box -dump the_new_world_h480p.mp4). It contains some information pertaining to a video track with a resolution of 848x352.
<TrackHeaderBox CreationTime="3223640787" ModificationTime="3223640788" TrackID="2" Duration="445300" Width="848.00" Height="352.00">
    <Matrix m11="0x00010000" m12="0x00000000" m13="0x00000000" m21="0x00000000" m22="0x00010000" m23="0x00000000" m31="0x00000000" m32="0x00000000" m33="0x40000000"/>
    <BoxInfo Size="92" Type="tkhd"/>
    <FullBoxInfo Version="0" Flags="1"/>
</TrackHeaderBox>
You also might have a look at the libraries, aimed at working with MP4 containers, that come with the MPEG4IP and MP4Box projects. 
Best regards,
Wesley De Neve
  ----- Original Message ----- 
  From: Adam Potolsky 
  To: Mp4-Tech Mailing List 
  Sent: Wednesday, August 30, 2023 12:50 AM
  Subject: [Mp4-tech] (no subject)
  Good day,
  I am in the process of creating some code to gather various forms of data from MP4 files, as well as, mpeg4 media content. Thus far I have been successful in parsing boxes to gather information like the title of the content (if present), etc. The difficulty I am having now is in trying to get more technical information such as the bitrate, and the height and width of a movie. Through my searches I have not found a source that describes how this kind of data can be extracted from a file. I assume it's inside the 'mdat' box data, but trying to figure out what to expect there form the thousands of pages of reference I have is very difficult. I have also looked through several source code solutions and they have been quite difficult to understand as they have lacked good source level comments and are not self documenting. 
  Is there a good source for this kind of information? Or, alternately, can anyone key me off to what I'm missing about how to read the various specs and code I have? (I have ISO/IEC 14496-lots, The MPEG Handbook, mplayer, the reference source from ISO, and more.)
  Thank you very much in advance for any help you can be.
  Adam Potolsky
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