Mpeg-1 to DivX/Xvid - what bit rate keeps the same quality?

[alexb76]

I have been playing in converting mpeg-1 to mpeg-4 DivX or Xvid for sometime now. I am still confused as what DivX 5.1 bit-rate the video quality would be the same as mpeg-1 1150kbps?

I am trying to reduce file sizes and don't know what is the best compromise between filesize and quality when converting from mpeg1 to DivX

Thnx

[johns0]

Just experiment and do 1 minute clips and set the bitrate to 500kbps up or down till you notice its the same quality.

[alexb76]

Just experiment and do 1 minute clips and set the bitrate to 500kbps up or down till you notice its the same quality.

I am trying but it's hard to do that... I guess I need to experiment more.

How much better quality do I get if I do 2-pass vs. 1-pass?

[State Of Mind]

It really depends on your source video, honestly. If you open your video in VirtualDub and go to File > File Properties, you will see "Average Data Rate". Whatever this is, use the same bitrate for the AVI. I _seriously_ suggest you use XviD, though. If you are willing to mess around with the bitrate, set it to 1000 and then down it by 50 each encode, but at a certain point, you will get smearing and such. If your MPEG-1 file is at 1100 kbps, then you can use that or even safely use 1000 for the XviD AVI.

Cheers,
Jeremy

[alexb76]

It really depends on your source video, honestly. If you open your video in VirtualDub and go to File > File Properties, you will see "Average Data Rate". Whatever this is, use the same bitrate for the AVI. I _seriously_ suggest you use XviD, though. If you are willing to mess around with the bitrate, set it to 1000 and then down it by 50 each encode, but at a certain point, you will get smearing and such. If your MPEG-1 file is at 1100 kbps, then you can use that or even safely use 1000 for the XviD AVI.

Cheers,
Jeremy

first - Happy New Year everyone

Second - if I use the same bitrate, then the file size will be virtually the same, so why would I go through all the hassle of converting if I am not gonna save any size?! I cant make it look better by going from mpeg1 to mpeg4...

I thought the whole idea of using mpeg4 and specially DivX/Xvid is to have the same quality of video at lower bit-rates and smaller file sizes. If for same quality I have to use the same bit-rate, what's the point of using mpeg4?

Thnx

[jimmalenko]

From a mixture of what I've read and my own experimentation, I believe that as an exceptionally general rule, and with no consideration of a number of variables, the "sweet spot" is somewhere between 2:1 and 3:1 for the MPEG to DivX/XviD bitrate comparisons, given an excellent source. There's a lot of exceptions here, but I believe that if you follow johns0's advice, and start with half the original bitrate, you'll find a similar result somewhere between 1/2 to 1/3 of the original bitrate. THere's no "magic" number, just approximations - mainly due to quality being so subjective.

The best advice I can give is to TRY IT YOURSELF. Experiment. See what works FOR YOU. That's the only thing that's important here

[alexb76]

From a mixture of what I've read and my own experimentation, I believe that as an exceptionally general rule, and with no consideration of a number of variables, the "sweet spot" is somewhere between 2:1 and 3:1 for the MPEG to DivX/XviD bitrate comparisons, given an excellent source. There's a lot of exceptions here, but I believe that if you follow johns0's advice, and start with half the original bitrate, you'll find a similar result somewhere between 1/2 to 1/3 of the original bitrate. THere's no "magic" number, just approximations - mainly due to quality being so subjective.

The best advice I can give is to TRY IT YOURSELF. Experiment. See what works FOR YOU. That's the only thing that's important here

Thnx... how you guys get 1:3 or 1:2 bitrates with good result? I have been converting 1150 mpeg1 kbps to Xvid 400-600 kbps both 1-pass and 2-pass, and I still cannot get same quality as the original. I can reduce the size considerably with a little quality loss, but haven't been able to get anywhere close to 1/3 bitrate!

Is it my source? I use latest Virtualdub, XviD-1.0.2, or DivX 5.2

[jimmalenko]

Thnx... how you guys get 1:3 or 1:2 bitrates with good result? I have been converting 1150 mpeg1 kbps to Xvid 400-600 kbps both 1-pass and 2-pass, and I still cannot get same quality as the original. I can reduce the size considerably with a little quality loss, but haven't been able to get anywhere close to 1/3 bitrate!

Is it my source? I use latest Virtualdub, XviD-1.0.2, or DivX 5.2

given an excellent source

1150kbps VCD is marginal quality at best. garbage in = garbage out, and IMO you're flogging a dead horse to try to get any significant filesize reduction in (you might get it down to half, but that would be the absolute most IMO). I think you need to look at your settings. What frame size is your source, and what frame size are you trying to convert to ?

[alexb76]

Thnx... how you guys get 1:3 or 1:2 bitrates with good result? I have been converting 1150 mpeg1 kbps to Xvid 400-600 kbps both 1-pass and 2-pass, and I still cannot get same quality as the original. I can reduce the size considerably with a little quality loss, but haven't been able to get anywhere close to 1/3 bitrate!

Is it my source? I use latest Virtualdub, XviD-1.0.2, or DivX 5.2

given an excellent source

1150kbps VCD is marginal quality at best. garbage in = garbage out, and IMO you're flogging a dead horse to try to get any significant filesize reduction in (you might get it down to half, but that would be the absolute most IMO). I think you need to look at your settings. What frame size is your source, and what frame size are you trying to convert to ?

Not changing any framesize, keep the same. Set XviD to whatever Kbps, 2-pass, all else default, and vollah!

[jimmalenko]

given an excellent source

1150kbps VCD is marginal quality at best. garbage in = garbage out, and IMO you're flogging a dead horse to try to get any significant filesize reduction in (you might get it down to half, but that would be the absolute most IMO). I think you need to look at your settings. What frame size is your source, and what frame size are you trying to convert to ?

Not changing any framesize, keep the same. Set XviD to whatever Kbps, 2-pass, all else default, and vollah!

Good, that's what I would do too. The first conversion from whatever the source was to VCD threw away quite a bit of the quality, and possibly introduced some artifacts. Because of this, you're trying to rake diarrhea up a hill IMO if you wish to even halve the filesize while retaining that quality. Now if you had a DVD source .... well, it's a different story altogether.

[alexb76]

given an excellent source

1150kbps VCD is marginal quality at best. garbage in = garbage out, and IMO you're flogging a dead horse to try to get any significant filesize reduction in (you might get it down to half, but that would be the absolute most IMO). I think you need to look at your settings. What frame size is your source, and what frame size are you trying to convert to ?

Not changing any framesize, keep the same. Set XviD to whatever Kbps, 2-pass, all else default, and vollah!

Good, that's what I would do too. The first conversion from whatever the source was to VCD threw away quite a bit of the quality, and possibly introduced some artifacts. Because of this, you're trying to rake diarrhea up a hill IMO if you wish to even halve the filesize while retaining that quality. Now if you had a DVD source .... well, it's a different story altogether.

Thnx. The videos are not perfect, downloaded off the net and do have artifacts.

I think I got a better picture when I did 2-pass (so hard to judge) I used to only do a 1-pass, now at around 600-700kbps, the quality is close enough to original. At half-size I lose stuff, so cant do, but I can probably manage a file of 60-70% size with same quality. I was just hoping for some more from XviD, I guess not!

[catdaddio6]

vcd is already a small format,,its hard to take something small and get smaller without loss...wmv might get you smaller,,not sure as i dont fool with it,,but those are usually pretty small files,,good luck with whatever ur doin