Need guidelines on audio and video bitrates for good quality

nunya · 19th September 2007, 16:24

I know my question is going to be a bit subjective and though I've read quite a bit of stuff on these forums, I'm having a tough time wrapping my brain around some of it.

Anyway, I recently did a vid quality test of my own taking a 20 minute clip from a movie. Using MEgui, x264, HQ-slowest profile and encoding it 4 times, twice at 700kbps using lanczos & lanczos4 and then twice again @ 2000kbps with same filters. And to be honest, just viewing it on my 23" lcd monitor I couldn't really tell a difference. I didn't mux an audio as I was just wanting to know if I could "see" a difference. Maybe I should have viewed it on the 42" plasma?

I guess what I'm looking to know is, that target file size of 2gb that I have been going by has yielded me fine results, but I'm wondering if that's even necessary if I'm not going to see much of a quality difference with a lower file size = lower bit rate.

I know everyone is different in their tastes and what they want, but are there video and audio bit rates that people generally use to get the best quality with minimum impact to file size? Again, this is pretty subjective, but at my stage of learning all this, I may be better off with some general guidelines as opposed to just "doing it".

Thanks for any advice.

I'll add that 98% of recenct encodings were xvid and only my last 2 were x264

danielkun · 19th September 2007, 16:38

There's a point where a certain encode looks transparent to your eyes, having higher bitrate than that could mean waste of bitrate.

Since you want to optimize the file size of your encodes, using constant quality should be better. Use CRF , where the encode has a constant quality through the whole video, but the final filesize is unknown, lower CRF numbers mean higher quality. From 18 to 22 is the "transparent" threshold, but you certainly use higher numbers to have lower filesize (I like CRF 24 for certain encodes for instance). Just try diferent numbers till you find the highest one that satisfies your needs, then use that CRF in every encode you make (you're targeting a fixed quality, not a fixed size).

In the x264 settings in MeGui, in the main tab, change the mode to "constant quality" and set the quality number.

You may find lots of post about CRF in the forum if you want to get more info about that.

nunya · 20th September 2007, 04:21

i just tried crf and the quality is horrible! i look up some more info on it.

Dark Shikari · 20th September 2007, 04:33

Quote:

Originally Posted by nunya

i just tried crf and the quality is horrible! i look up some more info on it.

What do you mean by "horrible"? Is it too blocky, or what? CRF 24 isn't particularly great; try 18 or 19 if you think that isn't enough. Find a good medium.

nunya · 20th September 2007, 05:59

forgive my dramatics.......i tried point(sharp) filtering over lanczos, so it looked very blocky. Redoing it with lanczos cleared it up. Using crf, set to 18, it looks okay but areas of the movie where it is dark has a purple hue to it. So right now, for experimentation and learning, i'm using the hq-insane profile with a bit rate of 1500 to see what it nets me quality-wise.

There is such a wealth of information out here but it's so damn confusing tryin to understand it all.

danielkun · 20th September 2007, 14:51

CRF doesnt introduce any artifacts that 2 passes wouldn't do at the same bitrate, it's only purpose is to dinamically asign the adecuate bitrate to each frame so that the quality stays constant throughout the whole video, I think that the purple hue is introduced by your script. Play the avs in media player classic or even in megui's own avs player (so it doesnt skip frames), go to the problematic part and check.

Try CRF 18-22 (there's a profile in megui CQ-ASP_Q2_eq(crf), use that). If the video gets blocky then use AQ (adaptive quantization), add these parameters in the "custom commandline options" in the "Zones" tab of x264 megui settings: --aq-strength 0.6 --aq-sensitivity 10 (if there's still blocking use instead: --aq-strength 0.5 --aq-sensitivity 5), AQ will increase your filesize quite a bit though.

CRF is also much faster than 2 pass encoding, something to consider, but if you're targeting a fixed filesize, stick to multi passes.

Atak_Snajpera · 20th September 2007, 16:08

Quote:

use instead: --aq-strength 0.5 --aq-sensitivity 0.5

It should be --aq-strength 0.5 --aq-sensitivity 5

danielkun · 20th September 2007, 17:06

oops, my bad.
fixed. Thanks

laserfan · 20th September 2007, 17:55

Quote:

Originally Posted by nunya

I recently did a vid quality test of my own taking a 20 minute clip from a movie. And to be honest, just viewing it on my 23" lcd monitor I couldn't really tell a difference. Maybe I should have viewed it on the 42" plasma?

When you convert programs you do it for some reason, right, whether that be for correcting issues with the original, or saving storage space, or streaming over a network, or for loading onto a portable device, etc. etc. In general what you want to do is to find those settings that look the best on the best display you will (ever?) use with that program, so if you're going to watch them on your 42" plasma well that is what you'd better be looking at to make your judgement about the encodings.

I've made a lot of recordings that look good on my 60" 1366x768 HDTV, but I wonder whether they will hold-up when my HT has a 10' screen and 1080p projector.

Having said all that, for making standard def encodings I tend to Xvid around 640x480 or 656x368 and 1200kbps, though I think that's overkill i.e. could be below 1000kbps easily. For making high-def I go for 720p and 3-4000kbps.

P.S. For audio, in SD encodings I usually just Stereo 128kbps or 160kbps, and for HD I leave the original AC3 track in-place.

microcosmos · 20th September 2007, 18:46

to predict the filesize and average bitrate I use a crf value that I think is good enough for a certain resolution and use it with avisynth's SelectRangeEvery().
I use more samples when the video is very varied to get a more accurate result.

I can't recommed a bitrate to use in general because that totally depends on the video,filters and settings. (I've had 320x240 grainy shaking camera filming the cat on grass video that needed 4000 kb/s or else it would get blocky...)

for audio I use nero aac with these settings: q 0.18 -hev2 (very small)

nunya · 20th September 2007, 22:03

well, it does seem that I may be using a higher bit rate than I really 'need' to be using, so I'll go ahead and start using a lower bit rate just to get a somewhate smaller file size. And start checking it on the wide screen.

I'm not an insane A/V kind of person, i just need something that looks and sounds good and I'm content, so in the end if I save some space that's only a plus.

I'll work those setting some more, though, the whole quantization thing, amongst other stuff, has turned my gray matter into mush.

thanks for the help.

19th September 2007, 16:24	#1 \| Link
nunya Registered User Join Date: Nov 2006 Posts: 29	Need guidelines on audio and video bitrates for good quality I know my question is going to be a bit subjective and though I've read quite a bit of stuff on these forums, I'm having a tough time wrapping my brain around some of it. Anyway, I recently did a vid quality test of my own taking a 20 minute clip from a movie. Using MEgui, x264, HQ-slowest profile and encoding it 4 times, twice at 700kbps using lanczos & lanczos4 and then twice again @ 2000kbps with same filters. And to be honest, just viewing it on my 23" lcd monitor I couldn't really tell a difference. I didn't mux an audio as I was just wanting to know if I could "see" a difference. Maybe I should have viewed it on the 42" plasma? I guess what I'm looking to know is, that target file size of 2gb that I have been going by has yielded me fine results, but I'm wondering if that's even necessary if I'm not going to see much of a quality difference with a lower file size = lower bit rate. I know everyone is different in their tastes and what they want, but are there video and audio bit rates that people generally use to get the best quality with minimum impact to file size? Again, this is pretty subjective, but at my stage of learning all this, I may be better off with some general guidelines as opposed to just "doing it". Thanks for any advice. I'll add that 98% of recenct encodings were xvid and only my last 2 were x264 Last edited by Guest; 19th September 2007 at 16:39. Reason: forum rule 9

19th September 2007, 16:38	#2 \| Link
danielkun Registered User Join Date: Aug 2002 Posts: 21	There's a point where a certain encode looks transparent to your eyes, having higher bitrate than that could mean waste of bitrate. Since you want to optimize the file size of your encodes, using constant quality should be better. Use CRF , where the encode has a constant quality through the whole video, but the final filesize is unknown, lower CRF numbers mean higher quality. From 18 to 22 is the "transparent" threshold, but you certainly use higher numbers to have lower filesize (I like CRF 24 for certain encodes for instance). Just try diferent numbers till you find the highest one that satisfies your needs, then use that CRF in every encode you make (you're targeting a fixed quality, not a fixed size). In the x264 settings in MeGui, in the main tab, change the mode to "constant quality" and set the quality number. You may find lots of post about CRF in the forum if you want to get more info about that. Last edited by danielkun; 19th September 2007 at 16:43.

20th September 2007, 14:51	#6 \| Link
danielkun Registered User Join Date: Aug 2002 Posts: 21	CRF doesnt introduce any artifacts that 2 passes wouldn't do at the same bitrate, it's only purpose is to dinamically asign the adecuate bitrate to each frame so that the quality stays constant throughout the whole video, I think that the purple hue is introduced by your script. Play the avs in media player classic or even in megui's own avs player (so it doesnt skip frames), go to the problematic part and check. Try CRF 18-22 (there's a profile in megui CQ-ASP_Q2_eq(crf), use that). If the video gets blocky then use AQ (adaptive quantization), add these parameters in the "custom commandline options" in the "Zones" tab of x264 megui settings: --aq-strength 0.6 --aq-sensitivity 10 (if there's still blocking use instead: --aq-strength 0.5 --aq-sensitivity 5), AQ will increase your filesize quite a bit though. CRF is also much faster than 2 pass encoding, something to consider, but if you're targeting a fixed filesize, stick to multi passes. Last edited by danielkun; 20th September 2007 at 17:06. Reason: typo in the commanline, thanks atak_snajpera :)

20th September 2007, 04:21	#3 \| Link
nunya Registered User Join Date: Nov 2006 Posts: 29	i just tried crf and the quality is horrible! i look up some more info on it.

20th September 2007, 05:59	#5 \| Link
nunya Registered User Join Date: Nov 2006 Posts: 29	forgive my dramatics.......i tried point(sharp) filtering over lanczos, so it looked very blocky. Redoing it with lanczos cleared it up. Using crf, set to 18, it looks okay but areas of the movie where it is dark has a purple hue to it. So right now, for experimentation and learning, i'm using the hq-insane profile with a bit rate of 1500 to see what it nets me quality-wise. There is such a wealth of information out here but it's so damn confusing tryin to understand it all.

20th September 2007, 17:06	#8 \| Link
danielkun Registered User Join Date: Aug 2002 Posts: 21	oops, my bad. fixed. Thanks

20th September 2007, 18:46	#10 \| Link
microcosmos Registered User Join Date: Sep 2007 Posts: 9	to predict the filesize and average bitrate I use a crf value that I think is good enough for a certain resolution and use it with avisynth's SelectRangeEvery(). I use more samples when the video is very varied to get a more accurate result. I can't recommed a bitrate to use in general because that totally depends on the video,filters and settings. (I've had 320x240 grainy shaking camera filming the cat on grass video that needed 4000 kb/s or else it would get blocky...) for audio I use nero aac with these settings: q 0.18 -hev2 (very small)

20th September 2007, 22:03	#11 \| Link
nunya Registered User Join Date: Nov 2006 Posts: 29	well, it does seem that I may be using a higher bit rate than I really 'need' to be using, so I'll go ahead and start using a lower bit rate just to get a somewhate smaller file size. And start checking it on the wide screen. I'm not an insane A/V kind of person, i just need something that looks and sounds good and I'm content, so in the end if I save some space that's only a plus. I'll work those setting some more, though, the whole quantization thing, amongst other stuff, has turned my gray matter into mush. thanks for the help.