WDM video capture guide

Here you will find some tips for capture with ATV2000 in WDM. Enter Capture mode and open configuration dialog by pressing F10 key. Here set main parameters:


Video size - set desired video capture resolution, for NTSC maximum resolution is 640x480 and for PAL 768x576. Some drivers, especially with BT848/878 chipsets, doesn't provide preview if vertical resolution is half of max lines or more. In that case you have to turn off preview or enable duplicating capture stream for preview.

Video encoding - must be set corresponding to desired compressor. Some compressors works best with YUV modes like MJPEG codecs (use YUY2) and other RGB modes (for example Indeo). Also if you are duplicating capture stream for preview and wants overlay, use YUY2 or UYVY mode for best performance (capturing in RGB mode will iniciate encoding conversion for preview, which is time consuming). Please be sure that not all capture devices supports all encoding models. Recommended encodings which offten wors are YUY2 and RGB24.

Framerate - framerate of video to capture. Typically you should set it to 25 fps for PAL/SECAM and 29.97/30fps for NTSC.

Preview size - video size displayed on monitor. It may be different than capture size, but not all drivers support it. You can also disable preview which will improve performance. Some drivers (BT848/878 cards) don't allow one of capture or preview stream be more than half áthe maximum lines (288 for PAl and 240 for NTSC). If this is the case, use "duplicate capture stream for preview"

Duplicate capture stream for preview - check if driver has no preview or has some limitation on preview ápin (see above)

If you want audio, select audio parameters too. Very important is Audio/Video Synchronization. Wrong setting will cause unsynchronized audio, bad performance or dropped frames.

Master stream - if your capture card has own audio capture with synchronized clocks, select None, if you use sound card for audio capture, select Audio. You should never set Video as master stream, but sometimes if the clock frequency of soundcard is lower then video capture card, you can try to select it.

Interleaving - AVI files contains both video and audio streams, which are interleaved by the amount of video frames (or time). áAlso precision of interleaving may be set. None will write frames and audio samples as it comes, it may cause bad disk performance. Full will everytime interleave by the selected amount of time/frames (may drop frames or samples if some rests in stream), Capture will try to interleave as Full, but will not hurry if not. Recommended value is Default (optimized values).



On the second page set compression for video and audio. You must take care of perfomance of your system (especially CPU and hard drive) to have CPU usage bellow 90% when selecting compressors or you will get dropped frames. For example capturing to DivX and MP3 with preview may be very CPU consuming. If CPU usage is close to 100%, decrease video size, capture uncompressedá audio or use different compressors. Fast and good quality comressors for video are MJPEG codecs (PIC, Morgan) and for audio ADPCM. Best compression gives DivX, MS-MPEG-4 and Indeo 5.11 codecs, resp. MP3 for audio. Config button will show dialog of Compressor, on VCM codecs the settings changed with it is saved. About button will show information about Compressor, if avaliable.