Digital VCR Video Capture

This is one of the most exciting features of the All-in-Wonder 128 and probably the primary reason for purchasing it. Video captures up to 720x480 resolution at 30 frames per second are possible from the coax TV, audio/video RCA, or the S-video inputs in any available format. To perform a video capture, all you have to do is hit the record button using the ATI Television program.

The card itself supports capturing in raw (uncompressed) YUV9, ATI VCR 1.0, ATI VCR 2.0, MPEG-1, or MPEG-2 video formats. The capture format that should be used varies depending on the intended use of the video and how much CPU power is available. Everyone can, of course, play raw uncompressed video, but the file sizes are simply unreasonable. In all cases, a hard drive capable of keeping up with the data being written is necessary. Raw video does require quite a bit of sustained hard drive performance.

The VCR 1.0 and 2.0 formats are proprietary ATI formats, but may be playable on other systems using AVI extensions. However, it is difficult (ie not possible with most software, including ATI's) to edit MPEG-1 or 2 video streams, making the VCR formats still very useful. According to ATI, this may change as MPEG formats increase in popularity. For distribution purposes, the final edited video can be saved in either of the two MPEG formats.

The best format for distributing video is most likely MPEG-1 since it is widely accepted and almost everyone has the appropriate CODEC for playback (it is now included in Microsoft's Windows Media Player). MPEG-1 provides approximately VHS level quality and is used in Video-CD's. The compression level is better than the ATI VCR formats and is more universally accepted. MPEG-2 is gaining popularity and will play using just about any software DVD player since DVD is just MPEG-2 video. Compression and quality levels are higher than that of MPEG-1, but of course require the most CPU power.

Of course, the available formats are heavily dependent on what CPU is in use. The following table, provided by ATI, gives the estimated CPU requirements for capture at 30 fps with CD quality 16-bit 44kHz audio using the various formats:

The "I frame" and "IBP frames" mentioned in the table above refer to the type of reference frames used by the MPEG compression. A good technical explanation of this and other MPEG issues is available here. IBP frames requires referring to the next frame in addition to the previous frame, which is obviously pretty complicated and, thus, requires more CPU power. MPEG-2 at 640x480 requires the SSE instructions of a Pentium III in order to accomplish 30fps capture if IBP frames compression is used. However, the advantage is obvious - the table above shows that the IBP frames method provides approximately double the compression of I frame alone.

Once size and compatibility considerations are taken into account, MPEG-1 with IBP frames compression is probably the most practical and does not require a very high-end CPU. To top it off, it is the smallest available format in terms of disk space. As mentioned above, MPEG-1 compression will give approximately VHS quality video. Of course, 640x480 MPEG-2 is absolutely gorgeous, near DVD quality, and if you've got the horsepower and disk space for it, that is definitely the way to go.

It is worth noting here that ATI's video compression algorithm is one of the few pieces of software that supports MMX and even SSE. In fact, the power of SSE is required for doing full 640x480 IBP frames MPEG-2 capture. Video capture with non-Intel CPU's is of course supported, but there are no optimizations for 3DNow! built into the current software. However, it is something ATI is looking into implementing in the future.

Users with low speed CPU's without MMX may want to simply stick with the All-in-Wonder Pro since you will not be able to take advantage of the improved compression methods supported by the All-in-Wonder 128.