Best bitrate for minimal quality loss?

[smackyourfupa]

I use Xmedia Recode to convert DVD's to mkv and usually set it at constant quantizer 18 (with audio copied) but sometimes the resulting file is actually bigger than the VOB file I ripped. Now I've been setting an average bitrate of 2000 and have been getting an output file of about 2GB but that seems a little large to me.

[Nelson37]

So lower the bitrate.

Acceptable quality is a judgement call.

[jagabo]

Now I've been setting an average bitrate of 2000 and have been getting an output file of about 2GB but that seems a little large to me.

file size = bitrate * running time

The whole reason you were using CRF encoding is because there's no way of knowing how much bitrate any particular video needs to retain "quality".

[Hoser Rob]

I haven't re encoded as many of my dvds here but I never had a larger file than the original with crf = 18. I suppose it's possible. Are these encodes from uncompressed dvd rips or rerips?

To me 2Gb from a dvd source isn't outrageously large for good quality. I've seen truly excellent encodes done from a bluray source in 2Gb or a little less but you can't get that quality from a dvd source. And you'd need a good knowledge of h.264 parameters to get that sort of quality.

I'd stick to crf/constant quality mode even though you can't accurately predict the output file size. It's just as good as 2 pass bitrate/size mode and a lot faster. That's especially important if you start to get into advanced h.264 settings. That's where the real meat is. But you can just scratch the surface and triple encoding time.

As mentioned, if you're happy with the quality of smaller files, just make them smaller.

[yoda313]

Fyi i'm sure the original poster is aware of this but any dvd with dts will be large. You mentioned audio is copied which I assume means no reencoding. So if its dts it will be larger then ac3.

At least on your dts dvds you can use the ac3 track to save a little space.

As mentioned, if you're happy with the quality of smaller files, just make them smaller.

Exactly that. You are the one that is going to be watching this so if you are ok with it go with that level.

Also I don't know if you have set a budget for it but I would seriously look into increasing your harddrive space.

Unless these are targeted for a tablet device with a finite memory space (unless you have a sd card slot then you can at least swap sd cards for extra space) you could easily go for larger file sizes without a problem.

I have recently purchased a toshiba 2tb harddrive for around 110.00 usd for my bluray rips. I'm leaving the video untouched and just reencoding the dts audio to ac3. At 25gbs a pop I don't care about space on my 2tb drive. I won't be converting all my blurays like this just my dts-ma discs.

Basically I'm trying to say if you are using an external or internal harddrive for these files I would seriously look at upgrading your storage space. Quite possibly you'll find the right price point in your budget and you can look into simply ripping the original dvd untouched and not bother with reencoding.

Again assuming your playback is a settop player that can do whole dvds in a folder or as an iso.

Fyi at least for an android based tablet the software player "daroon" can play a ripped video_ts folder exactly as if it was a disc in a dvd player. No conversion needed so long as you have enough storage space. You can rip the whole folder and copy to your sd card and play right away. Or you could shrink with dvd shrink and still retain good quality for tablet playback. I did this with an anime dvd set I had and was pleased with the results after shrinking it and copying the video_ts folder to the micro sd card.

I hope this has given you some ideas to improve or streamline your process. I know not everybody has the means or budget to simply go buy a new harddrive at a moments notice. But it is something to consider to save time on your video projects.

Edit - also if this is meant for playback on a tablet and you are using it at home (with a wifi network) you could look into streaming the files. Than you could use your computer and a large harddrive and stream that way. Then you would not need to worry about storage space on your tablet, just your computer.

Stream with playon, tversity or ps3mediaserver and you are good to go. Though you should really have wifi n if you are streaming high def video - which you aren't in this case since you say this is for dvds but n has more throughput than G so it wouldn't hurt for standard def.

[smackyourfupa]

I haven't re encoded as many of my dvds here but I never had a larger file than the original with crf = 18. I suppose it's possible. Are these encodes from uncompressed dvd rips or rerips?

To me 2Gb from a dvd source isn't outrageously large for good quality. I've seen truly excellent encodes done from a bluray source in 2Gb or a little less but you can't get that quality from a dvd source. And you'd need a good knowledge of h.264 parameters to get that sort of quality.

I'd stick to crf/constant quality mode even though you can't accurately predict the output file size. It's just as good as 2 pass bitrate/size mode and a lot faster. That's especially important if you start to get into advanced h.264 settings. That's where the real meat is. But you can just scratch the surface and triple encoding time.

As mentioned, if you're happy with the quality of smaller files, just make them smaller.

The encodes are from uncompressed DVD rips. I'm assuming crf is the same as constant quantizer? Maybe 1 out of every 6 or 7 encodes I will end up with a file larger than the original. So far I've been getting good results with a constant bitrate of 2000, but you're saying you think I should stick with constant quantizer (18) for good results, AND the speed will be tripled?

Fyi i'm sure the original poster is aware of this but any dvd with dts will be large. You mentioned audio is copied which I assume means no reencoding. So if its dts it will be larger then ac3.

At least on your dts dvds you can use the ac3 track to save a little space.

As mentioned, if you're happy with the quality of smaller files, just make them smaller.

Exactly that. You are the one that is going to be watching this so if you are ok with it go with that level.

Also I don't know if you have set a budget for it but I would seriously look into increasing your harddrive space.

Unless these are targeted for a tablet device with a finite memory space (unless you have a sd card slot then you can at least swap sd cards for extra space) you could easily go for larger file sizes without a problem.

I have recently purchased a toshiba 2tb harddrive for around 110.00 usd for my bluray rips. I'm leaving the video untouched and just reencoding the dts audio to ac3. At 25gbs a pop I don't care about space on my 2tb drive. I won't be converting all my blurays like this just my dts-ma discs.

Basically I'm trying to say if you are using an external or internal harddrive for these files I would seriously look at upgrading your storage space. Quite possibly you'll find the right price point in your budget and you can look into simply ripping the original dvd untouched and not bother with reencoding.

Again assuming your playback is a settop player that can do whole dvds in a folder or as an iso.

Fyi at least for an android based tablet the software player "daroon" can play a ripped video_ts folder exactly as if it was a disc in a dvd player. No conversion needed so long as you have enough storage space. You can rip the whole folder and copy to your sd card and play right away. Or you could shrink with dvd shrink and still retain good quality for tablet playback. I did this with an anime dvd set I had and was pleased with the results after shrinking it and copying the video_ts folder to the micro sd card.

I hope this has given you some ideas to improve or streamline your process. I know not everybody has the means or budget to simply go buy a new harddrive at a moments notice. But it is something to consider to save time on your video projects.

Edit - also if this is meant for playback on a tablet and you are using it at home (with a wifi network) you could look into streaming the files. Than you could use your computer and a large harddrive and stream that way. Then you would not need to worry about storage space on your tablet, just your computer.

Stream with playon, tversity or ps3mediaserver and you are good to go. Though you should really have wifi n if you are streaming high def video - which you aren't in this case since you say this is for dvds but n has more throughput than G so it wouldn't hurt for standard def.

Yes I'm aware dts is larger than ac3. As far as hard drive space, I have more than enough (around 15 TB). I am running XBMC on a Zotac Zbox as a dedicated HTPC with an external case housing 15 TB worth of HDDs connected via USB. As far as leaving video untouched, thats not something I would want to do. Most of the DVDs I rip and encode are between 6-7GB. I find if I rencode to h264 at 1.5GB to 2GB there is not much quality loss... I'm just wondering what the optimal settings are for best results.

[hello_hello]

CRF and constant quantizer are two different beasts. The latter will probably produce larger files as the quantizer value is fixed.
http://mewiki.project357.com/wiki/X264_Settings#qp

CRF = constant rate factor (constant quality). The quantizer value is varied by the encoder to produce a consistent visual quality. You should be using CRF rather than CQ. http://mewiki.project357.com/wiki/X264_Settings#crf

I haven't used XMedia Recode myself (I don't even know which encoders it uses), but if it doesn't have a CRF or constant quality mode for h264 encoding, then use something else.

I use MeGUI myself, but there's more "straightforward" encoder GUIs such as VidCoder. Whichever encoder GUI you use, a CRF value of 18 when using the x264 encoder (default encoder settings) is considered to be basically "transparent". The higher the CRF value, the lower the quality and the smaller the file size.

How large the final file size will be depends on how you resize the DVD before encoding and how hard it is to compress. Personally, I resize DVD video "up" to square pixel dimensions before encoding, so (cropping black bars not included) I'd resize a 16:9 NTSC DVD to 854x480 and a 16:9 PAL DVD to 1024x576. On average, using a CRF value of 18 and copying the original AC3 audio, the final file sizes generally average somewhere between 1.5GB and 2GB for me. That's just a rough average though.... there's always some video which will result in larger or smaller file sizes, but it'd be fairly rare for the final file size to be as large as the original.

If the average file sizes are still too large for you using a CRF value of 18, anything up to around CRF 23 should still look pretty good. And if the video is particularly noisy, running a noise filter over it while encoding will make it easier to compress and reduce the file size.

PS You shouldn't be using a constant bitrate either. CRF mode uses a variable bitrate in order to distribute more bits where they're needed and less where they're not to give you a higher visual quality for a given bitrate. If you want to select a bitrate when encoding, you should be using the 2 pass encoding mode (I don't know if Xmedia Recode has a 2 pass mode), which still lets you choose the (average) bitrate, but uses variable bitrate encoding as the CRF method does.
The difference between 2 pass encoding and CRF encoding is 2 pass lets you select the bitrate/file size in advanced but the quality will be unknown. CRF lets you select the quality but the file size will be unknown.

[smackyourfupa]

Instead of starting a new thread I'll just ask my next question here. I know DVDs have a res of 720x480 but the VOBs contain a flag so the picture is displayed at 853x480. My question is, when cropping out the black top/bottom bars and rencoding without altering the resolution, is that flag still kept somewhere in the resulting file (mkv in this case)? The last DVD I rencoded had a res of 720x464 after cropping out the black bars. If that flag is still embedded in my output file, the picture would be displayed at 853x480 but this would be incorrect because of the cropping I did. If the flag is not kept, then the resolution is displayed at 720x464 which is also incorrect. However, everything I've played the output file on has displayed it properly and I cant figure out how. Thanks for the help.

[jagabo]

The aspect ratio can be expressed as either the shape of individual pixels or the shape of the entire frame.

DAR = SAR * PAR

DAR = display aspect ratio, the final shape of the picture
SAR = storage aspect ratio, the frame dimensions
PAR = pixel aspect ratio, the shape of individual pixels

for example:

DAR = SAR * PAR
DAR = 720:480 * 8:9
DAR = 720/480 * 8/9
DAR = (720 * 8) / (480 * 9)
DAR = 5760 / 4320
DAR = 4/3
DAR = 4:3

Unfortunately, between MPEG 2 and MPEG 4 part 10 (AVC, h.264) the terminology changed to:

DAR = FAR * SAR

DAR = display aspect ratio, the final shape of the picture
FAR = frame aspect ratio, the frame dimensions
SAR = sample aspect ratio, the shape of individual pixels.

So the names have changed, but the calculations are the same. What used to be PAR is now called SAR.

On DVD the SAR and DAR are specified. The only allowable DAR values are 4:3 and 16:9. The PAR is implied by the above equation, rearragned: PAR = DAR / SAR. The shape of individual pixels doesn't change when you crop borders so you can specify the same PAR in your output file. Or you can specify the new DAR. Or you can resize the frame to give square pixels and set the pixel aspect ratio to 1:1 (if no aspect ratios are specfied players will assume square pixels).

To further complicate matters, there is a conflict between the MPEG 2 spec (used by DVD) and the ITU rec.601 digital video capture spec. In short, the MPEG 2 spec clearly states that the DAR refers to the entire 720x480 frame. The ITU spec says the DAR refers to the inner 704x480 portion of the frame and the 8 pixels on the left and right are just padding. In the end, the difference between the two specs is only about 2 percent and is usually ignored.

[hello_hello]

Instead of starting a new thread I'll just ask my next question here. I know DVDs have a res of 720x480 but the VOBs contain a flag so the picture is displayed at 853x480. My question is, when cropping out the black top/bottom bars and rencoding without altering the resolution, is that flag still kept somewhere in the resulting file (mkv in this case)? The last DVD I rencoded had a res of 720x464 after cropping out the black bars. If that flag is still embedded in my output file, the picture would be displayed at 853x480 but this would be incorrect because of the cropping I did. If the flag is not kept, then the resolution is displayed at 720x464 which is also incorrect. However, everything I've played the output file on has displayed it properly and I cant figure out how. Thanks for the help.

If you cropped a DVD to 720x464 and the encoded version is displaying correctly, it's no longer using a 16:9 aspect ratio. The new aspect ratio will be roughly 1.84, which is stored in the MP4/MKV file. Generally whether you resize or use anamorphic encoding (non-square pixels), or a combination of the two, a decent encoder GUI will calculate the correct resizing and/or aspect ratio for you, so the picture remains undistorted.

If you open a video with MPC-HC and use the File/Properties menu, it'll tell you the exact aspect ratio of the video (usually displayed as a fraction, I think). If only the storage aspect ratio (resolution) is displayed, then the video uses square pixels.

As Display Aspect Ratio = Storage AR x Pixel AR, when you change one, another must also change in order not to distort the picture. Generally the pixel aspect ratio is a constant if you use anamorphic encoding (it's possible to change it if you also change another value accordingly, but for the purpose of the explanation....) when you crop you change the storage aspect ratio (ie 720x464 instead of 720x480) and therefore the display aspect ratio must also change.

While not something you'd be likely to do in the real world, the most obvious example would be cropping half the height of the picture. The original 720x480 DVD has a display aspect ratio of 1.7777777 (16:9). If you crop it to 720x240 then what remains has a display aspect ratio of 3.555555.
If you resize to square pixels then you've changed the pixel aspect ratio to 1:1 and the display aspect ratio and the storage aspect ratio become one and the same (ie resizing a DVD to 854x480.

Anamorphic encoding (setting the display aspect ratio in the encoded video) is technically "better" than resizing to square pixels when encoding, as you're encoding the original video "as-is" but not all hardware players support aspect ratios in MKV/MP4 files and will display the video as though it uses square pixels. Rather than worry about whether a player will display the video correctly I gave up on anamorphic encoding and now resize to square pixels instead, but it's all personal preference.

[Cornucopia]

If you "cropped to 720x464", re-encoded & reauthored and was able to create a PLAYABLE DVD (in settop DVD players), then somewhere along the way (probably in the encoder) it ADDED what you cropped out (or alternately, resized) BACK to 720x480. Why? Because "DVD-Video" is a very strict spec and only allows 720x480 in NTSC (not counting ITU or 1/2D1 rez, etc). An encoder that is trying to be DVD compliant won't allow a 720x464 input to remain that way. If it had, it would have much trouble during playback.

So, behind the scenes and probably without telling you, it has undone what you tried to do. Don't believe me? Run the Playable DVD through MediaInfo and post the spec here.

Scott

[jagabo]

If you "cropped to 720x464", re-encoded & reauthored and was able to create a PLAYABLE DVD...

In his first post he said he was making MKV files. I imagine he's still talking about that.

[Cornucopia]

Not in post #8, where he says, "The last DVD I rencoded had a res of 720x464 after cropping out the black bars."

Scott

<edit>hmmm...unless he was talking about DVD being the input and (not stated, assuming) MKV being the output.
If so, then NeverMind.

[smackyourfupa]

If you open a video with MPC-HC and use the File/Properties menu, it'll tell you the exact aspect ratio of the video (usually displayed as a fraction, I think). If only the storage aspect ratio (resolution) is displayed, then the video uses square pixels.

I check file properties with MediaInfo, and the output files are still the same aspect ratio as the original DVDs (720x480) (thats if the AR is 1.77:1). If the original aspect ratio is 2.35:1, the output file is around 720x272. After encoding (with XMedia Recode), I then open the file in MKVMerge GUI and remove global flags, tags, etc. This why I am confused as to how the aspect ratio is still correct during playback.

Not in post #8, where he says, "The last DVD I rencoded had a res of 720x464 after cropping out the black bars."

Scott

<edit>hmmm...unless he was talking about DVD being the input and (not stated, assuming) MKV being the output.
If so, then NeverMind.

Sorry for not being clear. The DVD was the input, MKV output.
Anyway, I've been encoding videos for years. Started with AutoGK, now using XMedia Recode for the last few years. I am always happy with the results from XMedia Recode, just wanted to know how the correct aspect ratio was displayed after cropping/ removing flags, etc. Appreciate all the responses.

[jagabo]

You may have removed flags from the MKV header but the h.264 stream can still have AR flags. MMG will not remove those.

[hello_hello]

I check file properties with MediaInfo, and the output files are still the same aspect ratio as the original DVDs (720x480) (thats if the AR is 1.77:1).

Don't believe anything MediaInfo displays when it comes to aspect ratios as it does so much rounding I'm not sure why it bothers displaying anything at times. If you want to know the exact aspect ratio use MPC-HC as I described, or when you open the MKV with MKVMergeGUI it should tell you the display aspect ratio (or display dimensions) under the Format Specific Options tab (with the video stream selected).

If the original aspect ratio is 2.35:1, the output file is around 720x272. After encoding (with XMedia Recode), I then open the file in MKVMerge GUI and remove global flags, tags, etc. This why I am confused as to how the aspect ratio is still correct during playback.

According to my calculations, if a 16:9 NTSC DVD is cropped to 720x272, the remaining picture has an aspect ratio of roughly 3.2:1. If you crop a 4:3 NTSC DVD to 720x272, the aspect ratio will be around 2.4:1. You're not converting old 4:3 DVDs with a widescreen picture are you?

I'm not exactly sure what's going on, but maybe you could post a sample encode? Other than that, try this resize calculator. It's primarily designed to calculate resizing and aspect ratio distortion when you crop and resize to square pixels, but if you pick a particular type of DVD input and add your cropping it'll tell you the exact aspect ratio of the remaining picture. If you're not resizing to square pixels you can ignore the whole resizing section, but the source aspect ratio it displays should be the same as the aspect ratio in the encoded MKV file.
There's a check box labelled "Use ITU-R BT.601 Coeff". Checking it or unchecking it will change the aspect ratio a little. When it's checked it uses the "official" DVD resizing method, unchecked it uses straight 16:9 or 4:3 resizing. I've no idea which method XMedia Recode uses. Yoda Resize Calculator