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I have been working on video conversion. So, to find out video parameters I used ffprobe. However, when I run the command on an mp4 video file, I observe this:

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Total bitrate: 3547 Kb/s Video bitrate: 3512 Kb/s Audio bitrate: 32 Kb/s

Why total bitrate is 3 Kb/s more than the sum of audio and video bitrates?

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There are a few possibilities. MP4 is a container format and can contain more than just audio and video streams. While not all necessarily supported by MP4 specifically, container formats can contain things like sub-titles, sync data, chapter markers, meta-data, etc. They can also potentially contain more than one audio or video stream.

From the level of detail provided, it isn't really possible to tell exactly what is taking the extra space, it may just be overhead of the format itself or it could be some additional data stream that is stored within the container.

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I don't know for sure, but the total bitrate may be calculated as size / duration, which would include the container overhead. IOW the actual bit rate would be the sum of the two stream rates, with the container overhead shown as distributed over the entire length.

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  • Thanks! And is this container overhead same as metadata?
    – user2538255
    Commented Jun 17, 2014 at 11:58
  • As AJ points out, the container may carry other information. Some of this can be considered metadata, and some of it is actual data other than video or audio. The MediaInfo app would likely expose more of that than ffprobe.
    – Jim Mack
    Commented Jun 17, 2014 at 14:19
  • The MP4 container format is quite large in comparison to other container formats, it holds a lot of information which can sum up to quite a bit of data. You will probably see less of a difference in the total sum for longer videos.
    – timonsku
    Commented Jun 17, 2014 at 16:46

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