MeGUI: what bitrate values you use for 720p?

[TECK]

I looked at all the forums and decided is best to ask the question here. I originally tried StaxRip on few wedding videos, but I find MeGUI to suit better my encoding needs.

Because the recent play with video encoding, I decided to build a HTPC and transfer all my Bluray dvd's into. IMO, Windows Media Center looks great and will allow me to have all my movies centralized in one place, with a nice pictures, reviews, etc., beside Netflix.

I have it all figured with MeGUI and I'm very happy with the results.
For space reasons I decided to go with a 720p format. I performed 3 comparison tests for Spiderman movie:
1) Regular Bluray DVD movie
2) MeGUI MP4 container sized at 720p with 5950kbs high profile and a slow/tweaked preset of the above movie
3) Regular DVD of the above movie

The hardware used to compare the movie output was:
Sony 55" Bravia HX701 TV
Pioneer SC-37 7.1-Channel 3D Ready A/V Receiver
Pioneer BDP-23FD Bluray Player

First I compared the original Bluray output on my player with the .mp4 file. At 5950kbs, I was really surprised to see practically no difference to my eyes with the original Bluray disk. Then I compared the regular DVD with the .mp4 file, the differences were huge. The DVD looked granular, even when upscaled to 1080p.

Now, this is where I need your advice. I would like to set a standard for all my Bluray disks and encode each movie with the same bitrate (4950-5950kps). From your experience, do you think this value is appropriate? For example, I encoded the same movie at 3950kps and noticed minor details in certain scenes, so the extra 2000kb helped a lot.

I'm curious to find out your opinion, at what bitrate values you usually encode your movies. I'm also a little concerned with the space. My encoded video was 6.7GB with an AAC 448kbs audio file. Right now I have about 50 Bluray disks but my collection is growing faster since I purchased the new Sony TV. At 6GB/movie, it gives me in average 150 movies per terabyte. I plan to settle for 4950kps or higher, based in your input.

Thank you for sharing your knowledge.

[7ekno]

At 5950kbs, I was really surprised to see practically no difference to my eyes with the original Bluray disk.
Now, this is where I need your advice. I would like to set a standard for all my Bluray disks and encode each movie with the same bitrate (4950-5950kps). From your experience, do you think this value is appropriate?

There is alot of talk about bitrate, any reason for that?!?

CRF single pass encoding will be faster with the same quality at the same bitrate, the advanatage is you get to select a quasi "quality" number derivative ...

IMHO, you are better off doing 4 encodes at --crf 24, --crf 21, --crf 18 and --crf 15 and then comparing and see which one is closer to "transparent" for your eyes (--crf 16-18 is generally considered transparent, but test it yourself, I use --crf 17 for 720p stuff) ...

Using CRF also ensure "roughly the same quality" (so if you decide to your eyes that --crf 18 is "transparent", then --crf 18 is all you will need for 90% of your encodes!) ...

That way just makes more sense to me (imho of course) ...

7ek

[TECK]

Ya, I looked at the CRF settings. As you mentioned, 18 is transparent/lossless.
I thought that a 2 way pass with a decent bitrate will allow me to get a very good quality movie and huge savings of space, which is my goal after all.

Then, the bitrate factor wins over CRF. If that is the case, I want to know what bitrate values you usually set on a 2 way pass. Thanks.

[tebasuna51]

Each movie is different, using crf 18 with 720p I get bitrates between 3000-8000 Kb/s.

I can't recommend the same bitrate for all the movies, if you want use crf with a representative sample of the movie and after use the bitrate for the 2pass method.

[TECK]

> Each movie is different, using crf 18 with 720p I get bitrates between 3000-8000 Kb/s.
I see, I never knew that. I'm reading this MeGUI wiki (http://mewiki.project357.com/wiki/MeGUI/FAQ#What.27s_the_difference_between_Constant_Quantizer_and_Constant_Quality.3F) passage:
Note that a 1pass constant quality/quantizer encode will not look as good as a 2pass encode to the same filesize.

From what I read, they say a CFR 18 pass will not look as good as a 2pass. So we are back to square one, where I need to deal with a specific bitrate value. Based on tebasuna51's advice, I would do a CFR 18 on the movie, then use that bitrate indicator to perform a 2pass encode. Please let me know if I got this right.

I know 7ekno likes the CFR method... From your experience with the 2pass processing, do you think is worth the trouble or I should just stick with the Constant Quality mode set at 18?

Thank you.

[tebasuna51]

I can't see differences between 2 pass and crf mode (with x264, isn't the same with XviD), then I use always crf.

[nurbs]

Dark Shikari says: (http://forum.doom9.org/showpost.php?p=1373437&postcount=2396)
Given the same amount of encoding time, CRF is superior to 2-pass at the same bitrate. Given the same settings rather than the same time, they're effectively identical within margin of error. My recent tests show that CRF generally has a very slight edge, albeit the difference is so small that you'd have to have OCD to care.
There is another post where he lists the advantages and disadvantages of the two modes with more details, but I'm too lazy to look for it.

2-pass should be better than constant quantizer at the same bitrate since you turn off AQ if you use that.

[TECK]

Thank you guys, much appreciated. I will stick with the CRF method then.
Now that the video part is cleared, it is time to deal with the audio in MeGUI.

I plan to encode the DTS with Nero AAC. What options should I use?
I'm thinking to use this setup:

http://i54.tinypic.com/16m7ok5.png

My goal is to obtain a 448kbs stream, when checking the file with MediaInfo.
From my tests, I noticed that if I set the variable bitrate to Q=0.7 it outputs a higher value than 448kbs.

Let me know what settings you would suggest.

[hello_hello]

My goal is to obtain a 448kbs stream, when checking the file with MediaInfo.
From my tests, I noticed that if I set the variable bitrate to Q=0.7 it outputs a higher value than 448kbs.

You're using the same logic for audio encoding as you were for video encoding. The object should be to achieve a desired quality, not to obtain a particular bitrate. Using a particular quality setting the bitrate/file size will be whatever it needs to be (same as when using a CRF value for video encoding).

I use Q0.5 for all my AAC encoding. I think it's supposed to be the quality setting which is pretty much transparent, but someone else may be able to give you more specific information there.

As I don't use MeGUI to convert the audio myself, I have a question.... does the normalise peaks option normalise the audio in the traditional sense, or does it apply some sort of dynamic normalisation?

[Lyle_JP]

As I don't use MeGUI to convert the audio myself, I have a question.... does the normalise peaks option normalise the audio in the traditional sense, or does it apply some sort of dynamic normalisation?

It finds the peak volume and then sets that to 100%.

[TECK]

I believe dealing with a specific audio bitrate is different, compared to video.
I'm looking at it from an MP3 perspective, I want a specific bitrate. I don't think the audio quality is as important as video is. My question is: Do you think a 448kbs stream value is appropriate?

Please let me know what stream options you use and why. Thank you.

[tebasuna51]

Then you can change your perspective. MP3 and AAC are better with Variable BitRate and you need forget the average bitrate.

The recommended quality for Nero AAC is between 0.35 (source AC3 5.1 448 Kb/s or DTS 768 or MP3 V 5) and 0.5 (source AC3 5.1 640 Kb/s or DTS 1536 or MP3 V 2), 0.7 only if your source is lossless (but I use 0.5 also for lossless).

[TECK]

Thanks tebasuna51. Are Bluray's audio sources lossless by default?
There is one last technical detail: I need to know if you recommend the Normalize to 100%.

Thank you guys for the useful information.

[nurbs]

DTS-HD, Dolby TrueHD and WAV/PCM are lossless. All the other audio formats on Blu Ray are lossy. If you don't have an extra decoder eac3to can't decode DTS-HD and you'll end up with the lossy DTS core.

Normalizing only changes the volume, but not the quality. If you downmix you should normalize, if you don't it still shouldn't hurt.

[TECK]

Thanks nurbs. I don't plan to downmix the Bluray audio, I will always keep the original channels and sample rate. What will happen if I don't normalize but I keep a Q=0.5? Using logic, it will keep the original audio levels but lower the bitrate only. On the other hand, normalizing the audio will scale down any 120% audio segments to 100% by default.

If I have a peak of 120%, Normalize will adjust it to 100% but will not touch a 95% peak. Did I got it right?

Thanks for your patience guys, I promise this is the last question. :)

[tebasuna51]

...
If I have a peak of 120%, Normalize will adjust it to 100% but will not touch a 95% peak. Did I got it right?...

Source audio can't have 120% peaks, these peaks are only if you make some proccess like downmix, resample, ... with samples in float 32/64 bits.

BTW, if you have a 120% peak and use Normalize (eac3to or AviSynth) is converted to 100% and the previous 95% peak converted to 79.16%