xvid_encraw for first pass (ELDER method)

[ChrisBensch]

Is there any benefit/loss of using xvid_encraw for the first pass of an encoding session? The "ELDER" method uses it and it's quite fast, but I'm curious as to any reasons not to do so.

[berrinam]

Considering that this is the MPEG-4 AVC forum, I think Chris was talking about ELDER x264 using xvid (instead of x264) for the first pass, even when encoding x264.

I haven't done any tests, so I can only give you a theoretical answer: since xvid is not the same as x264, the bitrate allocation which xvid comes up with is not going to be the same as x264's. The result of that is that too much bitrate may be allocated to places which are easy for x264 to encode, and as a result, less bitrate to others, meaning that the overall quality could be less. Once again, that is just theoretical, so someone else will have to answer how much the real quality loss ends up being.

[foxyshadis]

Oops, forgot I wasn't in the xvid forum, sorry. ^^;

If you're just using xvid to chop up a video into encodable pieces and assigning a rough bitrate to them, it's negligible until you get really fine, like splitting at the GOP level. (x264's rate control gets very bad even for 2pass for such short stuff anyway. I just had to do a bunch of single-gop reencodes last week.) The only things that are really hard for xvid and really easy for x264 are fades, and those are usually pretty evenly distributed through a show.

[ChrisBensch]

Let me shed some light on why I'm asking. I started using ELDER x264 and have decided to improve upon the idea for my encodes at home. I'm still working out the encoding details but it's based on ideas from MeGUI and ELDER using multiple computers on a LAN. Although my setup works fine with x264 for both passes, going from 10fps w/x264 to 45fps w/xvid_encraw is of course nothing to overlook. I just refuse to sacrifice too much quality for speed.

[akupenguin]

10 vs 45? I get only a factor of 2 speed difference between xvid and x264 (both w/ fast 1st pass).

[ChrisBensch]

When I started with ELDER about 4 months ago that's what I was getting. I haven't redone them recently but tonight I'll try to find the time. Now that I think about it, ELDER was having trouble passing all of the right parameters. I'll see what I get with my setup.

[708145]

Is there any benefit/loss of using xvid_encraw for the first pass of an encoding session? The "ELDER" method uses it and it's quite fast, but I'm curious as to any reasons not to do so.

I reused the xvid 1st pass for the x264 encoding because it was easier to do.
Since then a real x264 first pass is on the todo.
Never tested what it costs quality wise.

bis besser,
T0B1A5

[ChrisBensch]

Ahh, gotcha, I guess I'll stick with x264. Thanks All!