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    <p>As you may be aware of, isom files are built out of atoms. Generally these are constructed</p> <pre><code>length (4 bytes), type (4 bytes), *body* </code></pre> <p>To get information about your encoded stream, you will need to parse the atoms containing the information you require. For the frame information, you will have to focus on the stbl. A great (shorter) introduction can be found in the quicktime format. The isom format has a few changes, but the general stuff (like frame information) is the same and it's freely available. More info here: <a href="https://developer.apple.com/library/mac/documentation/QuickTime/QTFF/QTFFPreface/qtffPreface.html" rel="nofollow">quicktime file format</a></p> <p>A short explanation: the stbl contains all sample information. The samples are grouped in chunks and stored in the mdat. One chunk could be a sample, but it could also be a group of samples (defined in the stsc). Each chunk has an offset regarding to the file start (defined in stco) and each sample has a size (defined in stsz). For sample timestamps, you can use the sample durations (defined in stts). To know which samples are keyframes, you can use the stss which lists the numbers of the samples which are key samples.</p> <p>So if you bring this all together: if you have a frame number and want to find the offset, look in the stsc to find the chunk which you need, look at the stco to find the offset of that chunk and add the sizes found in the stsz for the samples which are before the sample you need.</p>
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    1. POHow to find byte-offset in .mp4-file from timecode or framenumber?
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    1. POHow to find byte-offset in .mp4-file from timecode or framenumber?
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    1. COThanks for the very good and descriptive answer, it made how it all fits together clearer. I was having trouble seeing how to extract the needed info programatically from the boxes, but after reviewing the Bmff-code more I think I'll be able to piece it together from following your last paragraph and looking at the Bmff-code. Thanks again
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Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

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