GreenRomeo
27th August 2004, 06:34
Hi all,
After spending a week in reading carefully Doom9's final Xvid guide, Crusty's Xvid FAQs and, as Koepi has said many times to newbies, search throughout the Xvid forum, I didn't found enough the needed info for my problems. So now I post it here.
Unless you think that my question is dumb, or I was too lazy and need to take several week more to search through the forum with my poor English to find out the answers which take you only a few minutes to reply, please help me solving my problem, at least by give me a useful link. Thank you in advance.
And here it is.
MPEG or H.263?
Briefly, here is my question:
Should I used bitrate or size target to get the better quality in case output file size is not a strictly problem ? And if size target is chosed, what quantizer MPEG or H.263 should be used when I can't predict the ouput birate.
And below is what I specifically meant in the above question.
It is said vaguely in common Xvid guides that H.263 quantizer should be used in low bitrate and MPEG is suitable for high bitrate. But what is exactly "high" and "low" ? Is there a "threshold" such as 900 or 1500 kbps ... or it depends on each movies ?
I encoded my video file (WMV3, 640x272, 30fps, 1628 Kbps, ~1GB) to Xvid. My goal is preserving the quality as much as possible. First I used bitrate target and chosed the same value 1628 Kbps as the original. I think this is a high bitrate and hence used MPEG quantizer. The result is the size reduction of the ouput file is negligible, but the quality seems good.
But the Crusty's Xvid guide said that Size target should be used in any cases, so I tried to used it. I set a larger size (1.2GB against the original 1GB) hoping that will keep the quality better. The MPEG quantizer still be chosed. The result is weird. The ouput file size is not 1.2GB, but only 800MB, smaller than the original and even the previous ouput.
It seem Xvid has controlled the compression well when it wasn't sticked with a fixed average bitrate. But wait ... the ouput file's bitrate is now only 1050 Kbps (in my other tests with other source, this value is not constant but various: 1120, 849, 1100 kbps ...).
This result confused me because when I can not predict the output file size (as I choose file size target), it is clearly that I can not used the suitable quantizer: MPEG or H.263 (I even don't know exactly the standards we based to decide what is high or low bitrate).
After spending a week in reading carefully Doom9's final Xvid guide, Crusty's Xvid FAQs and, as Koepi has said many times to newbies, search throughout the Xvid forum, I didn't found enough the needed info for my problems. So now I post it here.
Unless you think that my question is dumb, or I was too lazy and need to take several week more to search through the forum with my poor English to find out the answers which take you only a few minutes to reply, please help me solving my problem, at least by give me a useful link. Thank you in advance.
And here it is.
MPEG or H.263?
Briefly, here is my question:
Should I used bitrate or size target to get the better quality in case output file size is not a strictly problem ? And if size target is chosed, what quantizer MPEG or H.263 should be used when I can't predict the ouput birate.
And below is what I specifically meant in the above question.
It is said vaguely in common Xvid guides that H.263 quantizer should be used in low bitrate and MPEG is suitable for high bitrate. But what is exactly "high" and "low" ? Is there a "threshold" such as 900 or 1500 kbps ... or it depends on each movies ?
I encoded my video file (WMV3, 640x272, 30fps, 1628 Kbps, ~1GB) to Xvid. My goal is preserving the quality as much as possible. First I used bitrate target and chosed the same value 1628 Kbps as the original. I think this is a high bitrate and hence used MPEG quantizer. The result is the size reduction of the ouput file is negligible, but the quality seems good.
But the Crusty's Xvid guide said that Size target should be used in any cases, so I tried to used it. I set a larger size (1.2GB against the original 1GB) hoping that will keep the quality better. The MPEG quantizer still be chosed. The result is weird. The ouput file size is not 1.2GB, but only 800MB, smaller than the original and even the previous ouput.
It seem Xvid has controlled the compression well when it wasn't sticked with a fixed average bitrate. But wait ... the ouput file's bitrate is now only 1050 Kbps (in my other tests with other source, this value is not constant but various: 1120, 849, 1100 kbps ...).
This result confused me because when I can not predict the output file size (as I choose file size target), it is clearly that I can not used the suitable quantizer: MPEG or H.263 (I even don't know exactly the standards we based to decide what is high or low bitrate).