First Pass Question

[ron spencer]

for V6 of DivX, is the FAST first pass suitable for first pass encode or does one really need to do the FULL pass. I gather either one is preferred than just one pass encode?

[Ranguvar]

Try with both, see if you notice a difference. Some do. Some don't.

[DigitAl56K]

ron spencer,

If you are trying to do a multi-pass encoding, unless you are trying to squeeze every last db of PSNR out of your encoding at the expense of much longer encoding times you should use the "Multipass 1st pass (fast)" mode during the first pass if you are trying to do a multipass (e.g. 2 pass, 3 pass) encoding.

Multipass isn't always preferable to a single pass encoding. Multipass is nice because when you know you have to hit a target file size it allows the encoder to best allocate the data to maintain a consistent quality throughout the file. However, if you are not particularly constrained by an output file size you might also want to try a "1-Pass quality-based" encoding. Here the "quantizer" setting is (in a nutshell) quite similar to a quality control, with lower quantizers giving you better quality but larger file sizes. How large will the output file be at a given quality? Well, that depends on the video you are encoding. If you choose a lower quantizer (i.e. higher quality) and the video contains a lot of fast motion then your file size will be large. On the other hand, if you choose a lower quantizer but the video is rather placid then you will still get high quality but with a lower file size. One trick I like to use (in the Pro version) is to go into the settings page, enable the feedback window, and in real-time adjust the quantizer gradually to see in advance what different settings are going to look like, and to graph the effect on data rate.

Try an encode in target quality mode with quantizer = 4, you should get a good balance between quality and compression, and under most circumstances the quality should be highly consistent.