IntroductionThe video compression manager (VCM) provides access to the interface used by installable compressors to handle real-time data. Typically applications use installable compressors to perform compressing and decompressing video data. The simplest solution for decompressing is using a DrawDib API, which is wraps all necessary functionality and provide a simple way for visualization of compressed images. The same approach has been used in MCIWnd for displaying an AVI files. All in all, looks like there is no reason to deal with low-level VCM API in most cases excepting:
- Processing a real-time video data from capture card with h/w codec
- Compressing/decompressing AVI file and writing results to the disk
- Compressing and decompressing single video image.
No comments about (1) and (2): this is the most usual way for utilizing VCM service.
CVidcclass presented below is intended for compressing and decompressing single video image, although it can be easy modified for any other purpose. I had a special reason for developing this class: in fact video codecs has an extremely high rate of decompression, no one from existing image compressors can compare with video codecs. At the same time, all of them are quite slow for compression. Thereby when you need to store many compressed images and provide the fastest reading, using the video codec seems to be the best solution.
Class implementation.CVidc class includes several methods from the list VCM services for compressing and decompressing single video image. Class does not support drawing (
ICDrawXXX) and sequence compressing (
OpenCompressor()method to initialize compressing, or suitable kind of
- Setup your callback function using
SetProgressCallback()method if you need a progress notification.
Decompress(). If you need to decompress single image from sequence
you can probably use
DecompressEx(), which accepts special flags( see SDK for more info).
- Close codec using
Class also provides a few services for querying format,
enumerating installed codecs, obtaining information from codec
and so on. See Vidc.h for more info.
Remark about capturing compressed video data.I can predict some questions about using of
CVidcfor capturing together with AviCap wrapper presented earlier.
I did not test this combination. You can try to use
DecompressEx()method with proper conversion of
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