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11th November 2018, 15:29 | #2 | Link |
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Even though this question probably is best answered by someone closer to the development of x265. But tbh I have seen very little improvements in both speed and/or quality for some time now, I have basically seen the same speed/quality for my use cases since the new lambda tables in 2.4. I have glanced on most of the patchnotes after that and from what i've seen most of them includes bug fixes and added features (chunk encoding this year for example), exluding the avx512 though, but the gains there was somewhat disappointing. I hope I'm wrong, but I view x265 to be very mature in these regards at this point.
Last edited by excellentswordfight; 11th November 2018 at 15:34. |
12th November 2018, 18:49 | #4 | Link |
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There have been some features that directly improve quality for some scenarios since 2.4. Also, performance improvements ARE quality improvements, because you can use a slower preset and get improved quality at the same encoding time. All the analysis reuse stuff can really speed up encoding a 12-stream adaption set. And chunked encoding is huge.
Specific to quality 2.5: --tune grain 2.7 --radl and --gop-lookahead 2.8 --refine-intra 4 and VBV Lookahead fix 2.9: fix rowStat computation and disable noise reduction with vbv Only the VBV Lookahead and rowStat fixes would be on by default in a basic encode; the others are context specific. Tune grain only for really grainy stuff, radl only for fixed GOP, and I'm not really sure what gop-lookahead is for (can't I just set --keyint and --min-keyint?). But all things together, on a good AVX512 capable system, for a lot of scenarios one can now use --preset-slower in the time that --preset slow took in 2.3. Heavily leveraging the analysis reuse for multibitrate encoding, I'm sure it can get up to 3-4x for some scenarios. |
16th November 2018, 17:40 | #6 | Link | |
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Those would both have a maximum GOP duration of 60 frames. Would the --gop-lookahead approach yield a bias towards having GOPs closer to 50 or something? |
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17th November 2018, 16:38 | #7 | Link |
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In theory --gop-lookahead option should work like that. It should bias to 50 and then sometimes extend it to 60 for a scenecut but I found that x265 likes to save bits by coding many scenechanges as P and not IDR/I so this option is basically useless.
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18th November 2018, 06:02 | #8 | Link | |
Derek Prestegard IRL
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What's the benefit of the chunked encoding method in x265?
I've always done this by simply using ffmpeg to encode chunks of a source and then stitching the result, e.g. Code:
ffmpeg -ss 30 -i input.mov -c:v libx265 -t 10 output.mp4 Quote:
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23rd November 2018, 23:09 | #9 | Link | |
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Might help some with stuff like weighted prediction as well, if GOP boundaries catch a transition partway through. |
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27th November 2018, 05:45 | #11 | Link |
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about chunked encoding: Would this be a good start for additional multi-threading option? Like 'virtually' splitting the source in chunks and encode them in parallel without having to physically split the source on systems where the cpu usage isn't that high?
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9th December 2018, 03:16 | #14 | Link | |
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x265 --seek 0 --crf 20 --fps 2400/1001 --keyint 240 --frames 1430 --y4m --preset slow "crim.mkv" --output 1.mkv and ffmpeg.exe -loglevel panic -i -strict -1 -f yuv4mpegpipe - | "x265.exe" --seek 0 --colorprim bt709 --transfer bt709 --colormatrix bt709 --crf 20 --fps 24000/1001 --min-keyint 24 --keyint 240 --frames 1430 --sar 1:1 --preset slow --ctu 16 --y4m --pools "+" --output "1.mkv" Laughs at me telling me it cannot open the source file |
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9th December 2018, 09:40 | #15 | Link | |
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Cu Selur |
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9th December 2018, 10:02 | #16 | Link | |
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Trying to figure out how best to encode pieces and chunked encoding as a feature caught my eye. Not seeing much documentation on it but saw seek and frames as possibilities. |
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10th December 2018, 21:30 | #17 | Link | |
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12th December 2018, 20:12 | #18 | Link |
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MCW has just checked in a bunch of improvements, after a long draught. Being able to use cutree in analysis reuse should help speed and quality in those scenarios somewhat. Also a new parameter to make muxing after chunked encoding a lot easier. The other stuff is for Dolby Vision, including QP tuning for Y'CtCp.
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18th December 2018, 06:03 | #19 | Link | |
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To automate this is going to take me some time but it's my goal, best of all this seems to be using all cross platform tools so in theory my Windows and Linux machines can all play together. However... Reading some I see there's a new feature named chunk, an advantage to this appears to be that it reads ahead and after the given start/stop frames which is an advantage to the encoder's prediction and analysis - yes? It appears to be geared towards exactly what I'm attempting to do. However when I attempt to use it I receive errors that it must be used on a "closed GOP" structure. I understand that this has to do with the way that frames are written/sequenced in the video but I'm not sure how to satisfy this option or how I might pull out good starting and stopping points as I did with ffmsindex. Google isn't helping me much I'm afraid Little help for the newbie please? I'd make this a separate post but this was one of the sparse few threads I've found that mention chunking and thus far I've found no examples using it <sigh> Bonus question - if I'd like to trim off black bars around a video as say HandBrake does how best to do this with something cross-platform? |
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