I’ve been using ffmpeg with libx265 to transcode Star Wars blurays to smaller files. Episodes 1 and 2 went perfectly. I made screenshots from identical points and they were virtually indistinguishable.
When I did Episode 3, I noticed that the screenshots from the transcode were darker than the source. I thought it was a problem with x265 and posted a ticket with them. To prove it was(n’t) x265, I had to first convert a minute to raw YUV in ffmpeg, then use the x265 command line to transcode as I had done previously, resulting in an HEVC stream. When I compared screenshots from the YUV and HEVC streams, they were indistinguishable, but both were darker than the source. In other words, ffmpeg apparently was doing something to make the video darker, both when transcoding and converting to raw video. This happened with Episode 3 but not 1 and 2. Unfortunately I can’t attach the screenshots here, but here are links to them: one from the source and other from the ffmpeg transcode. You might have to rock back and forth between them, then the difference is obvious. https://www.dropbox.com/s/5anl2l17hl75t73/source.png?dl=0 <https://www.dropbox.com/s/5anl2l17hl75t73/source.png?dl=0> https://www.dropbox.com/s/q83buel9792gmjd/transcode.png?dl=0 <https://www.dropbox.com/s/q83buel9792gmjd/transcode.png?dl=0> And here is a minute from the source (216 MB with original video but squashed audio): https://www.dropbox.com/s/h1a5yird75n3am6/Episode3_1minute.mkv?dl=0 <https://www.dropbox.com/s/h1a5yird75n3am6/Episode3_1minute.mkv?dl=0> Below is the original ffmpeg commandline and initial output for the first pass. The source is an mkv with streams copied from the bluray (for my own use). ffmpeg -i in.mkv -pass 1 -map 0 -c:v libx265 -b:v 3M -an -sn -f matroska -y /dev/null && \ ffmpeg -i in.mkv -pass 2 -map 0 -c:v libx265 -b:v 3M -c:a copy -c:s copy -y out.mkv ffmpeg version N-76705-g35bbc19 Copyright (c) 2000-2015 the FFmpeg developers built with Apple LLVM version 7.0.0 (clang-700.1.76) configuration: --prefix=/Volumes/Ramdisk/sw --enable-nonfree --enable-gpl --enable-version3 --enable-libmp3lame --enable-libx264 --enable-libx265 --enable-libgsm --enable-libvpx --enable-libfdk-aac --enable-libvorbis --enable-libass --enable-libfreetype --enable-libfontconfig --enable-libfribidi --disable-outdevs --disable-ffserver --disable-network libavutil 55. 6.100 / 55. 6.100 libavcodec 57. 15.100 / 57. 15.100 libavformat 57. 15.100 / 57. 15.100 libavdevice 57. 0.100 / 57. 0.100 libavfilter 6. 15.100 / 6. 15.100 libswscale 4. 0.100 / 4. 0.100 libswresample 2. 0.101 / 2. 0.101 libpostproc 54. 0.100 / 54. 0.100 [matroska,webm @ 0x7fa85380a600] Could not find codec parameters for stream 5 (Subtitle: hdmv_pgs_subtitle): unspecified size Consider increasing the value for the 'analyzeduration' and 'probesize' options [matroska,webm @ 0x7fa85380a600] Could not find codec parameters for stream 6 (Subtitle: hdmv_pgs_subtitle): unspecified size Consider increasing the value for the 'analyzeduration' and 'probesize' options Input #0, matroska,webm, from 'in.mkv': Metadata: title : Star Wars Episode III. Revenge of the Sith encoder : libmakemkv v1.9.7 (1.3.0/1.4.1) darwin(x86-release) creation_time : 2015-12-17 18:10:26 Duration: 02:20:05.89, start: 0.000000, bitrate: 34490 kb/s / ******** Chapter list deleted *********** / Stream #0:0(eng): Video: h264 (High), yuv420p, 1920x1080 [SAR 1:1 DAR 16:9], 23.98 fps, 23.98 tbr, 1k tbn, 47.95 tbc Metadata: title : Video Stream #0:1(eng): Audio: dts (DTS-HD MA), 48000 Hz, 6.1, fltp (default) Metadata: title : DTS-HD Master Audio 6.1 Stream #0:2(eng): Audio: ac3, 48000 Hz, stereo, fltp, 224 kb/s Metadata: title : Commentary by George Lucas, Rick McCallum, Rob Coleman, John Knoll and Roger Gayetta Stream #0:3(eng): Audio: ac3, 48000 Hz, stereo, fltp, 224 kb/s Metadata: title : Commentary from archival interviews with the team of actors and crew Stream #0:4(eng): Subtitle: hdmv_pgs_subtitle, 1920x1080 Metadata: title : Full English Subs Stream #0:5(eng): Subtitle: hdmv_pgs_subtitle Metadata: title : Commentary 1 Speaker ID Subs Stream #0:6(eng): Subtitle: hdmv_pgs_subtitle Metadata: title : Commentary 2 Speaker ID Subs x265 [info]: HEVC encoder version 1.8+1-5dcc9d3a928c400b x265 [info]: build info [Mac OS X][clang 7.0.0][64 bit] 8bit x265 [info]: using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 x265 [info]: Main profile, Level-4 (Main tier) x265 [info]: Thread pool created using 4 threads x265 [info]: frame threads / pool features : 2 / wpp(17 rows) x265 [info]: Coding QT: max CU size, min CU size : 64 / 8 x265 [info]: Residual QT: max TU size, max depth : 32 / 1 inter / 1 intra x265 [info]: ME / range / subpel / merge : hex / 57 / 2 / 2 x265 [info]: Keyframe min / max / scenecut : 23 / 250 / 40 x265 [info]: Lookahead / bframes / badapt : 20 / 4 / 2 x265 [info]: b-pyramid / weightp / weightb : 1 / 1 / 0 x265 [info]: References / ref-limit cu / depth : 3 / 0 / 0 x265 [info]: AQ: mode / str / qg-size / cu-tree : 1 / 1.0 / 32 / 1 x265 [info]: Rate Control / qCompress : ABR-3000 kbps / 0.60 x265 [info]: tools: rd=3 psy-rd=0.30 signhide tmvp strong-intra-smoothing x265 [info]: tools: deblock sao Output #0, matroska, to '/dev/null': Metadata: title : Star Wars Episode III. Revenge of the Sith encoder : Lavf57.15.100 / ******** Chapter list deleted *********** / Stream #0:0(eng): Video: hevc (libx265), yuv420p, 1920x1080 [SAR 1:1 DAR 16:9], q=2-31, pass 1, 3000 kb/s, 23.98 fps, 1k tbn, 23.98 tbc Metadata: title : Video encoder : Lavc57.15.100 libx265 Stream mapping: Stream #0:0 -> #0:0 (h264 (native) -> hevc (libx265)) Press [q] to stop, [?] for help frame= 188 fps=5.3 q=-0.0 size= 6986kB time=00:00:06.58 bitrate=8685.6kbits/s _______________________________________________ ffmpeg-user mailing list [email protected] http://ffmpeg.org/mailman/listinfo/ffmpeg-user
