What Codec?

[EZ-Fan]

I am looking to capture some long VT (1-2 Hrs) on my PC using Noel's AMCap, problem is I only have a Pentium 4, 2.8Ghz!



I would like some experienced people to suggest some free video/audio codecs that are low on CPU usage, fast enough for realtime encoding and also offer lossless video quality.

Any ideas


Cheers!

[jagabo]

HuffYUV, PicVideo MJPEG

[EZ-Fan]

Thanks for the suggestions! I was hoping for something more modern than HuffYUV, any ideas?

[edDV]

Thanks for the suggestions! I was hoping for something more modern than HuffYUV, any ideas?

Assuming you want quality, you need a hardware codec (e.g. Hauppauge PVR), a low CPU intensive intermediate format (e.g. HuffYUV, MJPEG, Cineform), a high bitrate real time MPeg2 encoder (e.g. MainConcept*) or a RAID to assist uncompressed capture.

You can sacrifice quality to make software MPeg2 capture possible. Compromises wouldl be I frame resolution, motion detection, etc. resulting in more blocks and pixelization. Better to encode as a second step.


* A 2.8 P4 is good for about 7Mb/s CBR MPeg2 single pass with reasonable quality. Pushing compression to 6Mb/s may cause rebuffer and/or buffer overflow. Review your capture.

[sanlyn]

Thanks for the suggestions! I was hoping for something more modern than HuffYUV, any ideas?

EdDv (see above) is on the right track. A 2.8 GHz P4 should not be a problem. In fact, with a good compressor many people do quite well with 2.0 GHz, and not much better with faster CPU's. You should have at least 1.5-GB RAM, with 2-GB noticeably better.

I don't understand what you mean by a "more modern" codec than huffyuv. Unless you're getting into highly sophisticated gear starting at $100,000 with custom software, huffyuv is a standby in its class. It fulfills the requirements you previously listed:

- low on CPU usage
- fast enough for realtime encoding
- offers lossless video quality

Huffyuv is adept in all three areas. No, it is not absolutely 100% "lossless" -- but neither is any other compression codec. Huff's compression is so efficient it is technically described as "lossless". I detect no difference between an uncomprerssed AVI and one compressed and re-compressed up to 3 generations with huffyuv; beyond 3rd gen or so, you'll see signs of grain and slight desaturation (in other words, a 3rd-generation huffyuv will start looking like a first-generation XVid or WMV). Try 3 or 4 generations with other video compressors and see what you get. You can avoid processing losses by running intermediate, multiple processing steps using uncompressed AVI, then converting the final product to huffyuv.

[jagabo]

Huffyuv... is not absolutely 100% "lossless" -- but neither is any other compression codec.

HuffYUV is absolutely lossless when working with YUY2 video (virtually all capture devices without hardware encoders capture YUY2 or some other YUV 4:2:2 format). If you were getting losses it was somewhere else along your encoding chain. Likely RGB to YUV conversion by your editor. Lagarith (compresses better but is slower) is also lossless when working with YUY2.

I just took an uncompressed YUY2 video, sequentially compressed it with HuffYUV 10 times in a row with VirtualDub in Fast Recompress mode and the final output was bit-for-bit identical to the source.

[JohnnyMalaria]

Nothing wrong with HuffYUV - it is essentially JPEG without the quantization stage. DV, MPEG and other common compression schemes use the same basic algorithm.

A Pentium 4 2.8GHz is plenty enough. Even a 1.5GHz Pentium M laptop can do realtime processing of DV (which is JPEG-esque).

[sanlyn]

Huffyuv... is not absolutely 100% "lossless" -- but neither is any other compression codec.

HuffYUV is absolutely lossless when working with YUY2 video (virtually all capture devices without hardware encoders capture YUY2 or some other YUV 4:2:2 format). If you were getting losses it was somewhere else along your encoding chain. Likely RGB to YUV conversion by your editor. Lagarith (compresses better but is slower) is also lossless when working with YUY2.

I just took an uncompressed YUY2 video, sequentially compressed it with HuffYUV 10 times in a row with VirtualDub in Fast Recompress mode and the final output was bit-for-bit identical to the source.

Correct again, jagabo. I start with YUY2 and avoid any and all color space conversion whenever possible. Many hobbysists aren't as careful as some of us .

[jagabo]

Also, both HuffYUV and Lagarith also have lossless RGB modes.