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Old 14th July 2015, 17:23   #11  |  Link
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Originally Posted by De_Hollander View Post
Alle x264 re-encodes haves 4.1 flag.
That's not true. It is true that most encoding in h264 are in 4.1 (or 4.2) level, because 4.1 is the level of the BDs, and therefore most hardware players are compatible with that level. But most is not all. You can find encodings in level 5.0 or 5.1, but they are less popular, because very few hardware players support them. Level 5.0 is even necessary if you encode in full-SBS or full-T&B.
Originally Posted by De_Hollander View Post
what's it meanss BD compatibility flag in your program anyway ?
The BD standard imposes certain limitations to the encodings, so that the hardware players do not need too large memory buffers or too fast hardware, in order to reduce the cost of the hardware players (and probably because level 4.1 was the current h264 level when the BD standard has been written). If you want to import the movie in a BD authoring tool, you have to encode it with the options that restrict the encoding to the BD level. The BD level is similar to level 4.1, but with a smaller maximum bitrate, and other limitations. Therefore, it is not sufficient to specify level 4.1 to be BD compatible. The flag in BD3D2MK3D sets the --bluray-compat as well as a bunch of other settings to respect the BD standard. If you want to know exactly what it sets, generate a project with the BD compatible option on, and then another one with the flag off, and compare the x264 commands in the _ENCODE.cmd files.

Anyway, if you do not want to build a blu-ray with your SBS, you don't need to set that flag. (Some peoples set it anyway to be sure to be compatible with all TVs and other hardware players, but IMO that's not necessary. Level 4.1 or even level 4.2 are accepted by the vast majority of players.) And anyway, if you set the CRF value to a very low level, it CANNOT be compatible with the BD standard, because the bitrate will be way to high. Therefore, I suggest to do your next encodings without the BD compatible flag, and with level 4,1 or 4.2 alone.
Originally Posted by De_Hollander View Post
I would like to have bitrate of 13
the intention is to have a smaller file than the blu-ray with a bit rate of 13 to save hard disk space.
13 is not a valid bitrate. You mean CRF 13, right? Anyway, if you specify the CRF (or CQ) mode, you cannot control the bitrate precisely. The encoder will take the decisions for you, according to the complexity of the movie. A very simple CGI animated movie for kids may be encoded with a very low bitrate with CRF 13, but a live film with many details and action scene will probably require a much greater bitrate for the same CRF. In both case, the final quality will be roughly equivalent, because the encoder will have taken the right decisions. In other word, specifying the CRF is roughly equivalent to specify the quality you want, while specifying the bitrate doesn't ensure a constant quality and, as I wrote above, should be used to specify the final file size only.
Originally Posted by De_Hollander View Post
normaly 2 pass re-encoding is in the most re-encodings x264 program's the best option voor quality.
Totally wrong.

I agree that encoding in bitrate mode in 1 pass is the worst thing to do, because since h264 is a variable bitrate codec. Therefore, there is no way to know in advance what will be the ideal bitrate for each part of the movie. For example, if the movie is simple and has not many moving scenes at the beginning, the encoder will have much bitrate to waste. It will assign a bitrate to the easy scenes in order to have a final AVERAGE bitrate equal to the bitrate specified in the command line. But now imagine that the last part of the movie is terribly complex and has many action scenes (like in many action movies). The encoder will have already spent a big part of the bitrate to encode the easy parts, and it will have to encode the final scenes with the remaining bitrate, a too low bitrate for that difficulty. The quality of the end of the movie will be terrible!

Why is 2-pass is better than ABR? During the first pass, the encoder analyses the difficulty to encode each shot and image in the film, with a simplified encoding, and it saves a stats file. During the second pass, it uses the stats file to distribute the bitrate according to the difficulty of the different parts. That way, it can keep the bitrate for the difficult parts, and encode the easy parts with a smaller bitrate. That's a good solution, but note two things:
1) The first pass uses only a faster encode to estimate the difficulty. Therefore, it is not exactly as accurate than the second pass, and small errors in the bitrate distribution are still possible. Therefore, the 2-pass encoding is NOT perfect.
2) Using 2-pass makes sense ONLY if you need a specific file size. If you do NOT specify the file size (or, in other words, the bitrate), the encoder does NOT need to restrict itself to a certain overall bitrate, and therefore it will give EXACTLY what is necessary to obtain the best quality, during the first and only pass. Therefore, encoding in CRF mode gives PERFECT results in only one pass, and it's certainly better that GOOD results in two passes. It's also much faster.
I agree that many encodings are made in 2-pass, and you can read misleading howtos on the net that explain that 2-pass is better. It's simply absurd. Peoples think it must be better, because it's longer, but in fact, it's slightly less good.
Note also that some encoders do NOT have CRF or CQ options and REQUIRE to give a precise bitrate. It's the case, for example, of DVD-Fab. Since in that case, you can only encode in ABR or 2-pass, it is obviously better to use the 2-pass mode. But it's only because that encoder is very limited. With x264, you don't have that limitation.
Originally Posted by De_Hollander View Post
and cpu re-encoding gives the best results than GPU acceleration.
I agree on this.
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Last edited by r0lZ; 14th July 2015 at 17:25.
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