HDV media is repaired without major problem. A sample of a good file is often needed.
It is often necessary, and always helpful, to have a good HDV file similarly encoded. Even if the file contains only a few frames, the fact that it was encoded with the exact settings of the damaged file will provide useful information:
- Sample description (usually in the stsd atom)
- Pixel size (HDV 720, HDV 1080)
- Composition offsets (ctts table)
This information can be guessed from a damaged file, but through a very lengthy trial-and-error iterative process.
How to repair a corrupt HDV movie
The easiest way is certainly to ask our Movie Repair Service to do it for you.
But for those who can program, here you have a few tips:
Techniques used are:
- Patching of the file with a sample description from a good file
- Frame reordering
- Audio Scraping
Video track has a 'hvdx' codec fourcc (where x can take many values, see table below) and is organized in keyframes and inter-frames. HDV frames are not stored in playback order, so there is a ctts table that specifies the offset between decode time and display time.
Note that we also find two tables called cslg and sdtp (sample dependencies) but these are optional: the movie works perfectly without them. In repairs we usually don't bother with recreating those tables.
Audio tracks often come in raw PCM 'sowt' of 'twos' formats, for example 48kHz stereo 16 bits.
Repair process consists of reindexing video frames. Note that as 'hdv4' is not available as compressor, the repaired file has to be bootstrapped from a valid one.
Frame reordering is possible if the pattern is predictable. Otherwise, the result will be shaky.
Flavors of HDV
HDV flavor is determined by stsd atom of video track, whose fourcc can take many different values.
For example, HDV 720p30 stands for: resolution 1280x720, progressive, 30 frames per seconds. i stands for interlaced.