#6570(avfilter:new): loudnorm filter changes sample rate
#6570: loudnorm filter changes sample rate ----------------------------------+-------------------------------------- Reporter: slhck | Type: defect Status: new | Priority: normal Component: avfilter | Version: git-master Keywords: loudnorm | Blocked By: Blocking: | Reproduced by developer: 0 Analyzed by developer: 0 | ----------------------------------+-------------------------------------- The `loudnorm` filter changes the sample rate of the input output stream, sometimes doubling it, sometimes it will be even higher. The desired behavior would be that the sample rate remains the same. {{{ ./ffmpeg -f lavfi -i anullsrc=r=48000 -filter:a loudnorm -t 1 out.wav ffmpeg version N-86910-g797c232-tessus Copyright (c) 2000-2017 the FFmpeg developers built with Apple LLVM version 8.0.0 (clang-800.0.42.1) configuration: --cc=/usr/bin/clang --prefix=/opt/ffmpeg --extra- version=tessus --enable-avisynth --enable-fontconfig --enable-gpl --enable-libass --enable-libbluray --enable-libfreetype --enable-libgsm --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopus --enable-libsnappy --enable- libsoxr --enable-libspeex --enable-libtheora --enable-libvidstab --enable- libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libx264 --enable-libx265 --enable-libxavs --enable-libxvid --enable-libzmq --enable-libzvbi --enable-version3 --disable-ffplay --disable-indev=qtkit libavutil 55. 69.100 / 55. 69.100 libavcodec 57.102.100 / 57.102.100 libavformat 57. 76.100 / 57. 76.100 libavdevice 57. 7.100 / 57. 7.100 libavfilter 6. 95.100 / 6. 95.100 libswscale 4. 7.101 / 4. 7.101 libswresample 2. 8.100 / 2. 8.100 libpostproc 54. 6.100 / 54. 6.100 Input #0, lavfi, from 'anullsrc=r=48000': Duration: N/A, start: 0.000000, bitrate: 768 kb/s Stream #0:0: Audio: pcm_u8, 48000 Hz, stereo, u8, 768 kb/s Stream mapping: Stream #0:0 -> #0:0 (pcm_u8 (native) -> pcm_s16le (native)) Press [q] to stop, [?] for help Output #0, wav, to 'out.wav': Metadata: ISFT : Lavf57.76.100 Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 192000 Hz, stereo, s16, 6144 kb/s Metadata: encoder : Lavc57.102.100 pcm_s16le size= 750kB time=00:00:01.00 bitrate=6144.8kbits/s speed=6.65x video:0kB audio:750kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.013281% }}} {{{ ./ffmpeg -f lavfi -i anullsrc=r=44100 -filter:a loudnorm -t 1 -c:a aac out.m4a ffmpeg version N-86910-g797c232-tessus Copyright (c) 2000-2017 the FFmpeg developers built with Apple LLVM version 8.0.0 (clang-800.0.42.1) configuration: --cc=/usr/bin/clang --prefix=/opt/ffmpeg --extra- version=tessus --enable-avisynth --enable-fontconfig --enable-gpl --enable-libass --enable-libbluray --enable-libfreetype --enable-libgsm --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopus --enable-libsnappy --enable- libsoxr --enable-libspeex --enable-libtheora --enable-libvidstab --enable- libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libx264 --enable-libx265 --enable-libxavs --enable-libxvid --enable-libzmq --enable-libzvbi --enable-version3 --disable-ffplay --disable-indev=qtkit libavutil 55. 69.100 / 55. 69.100 libavcodec 57.102.100 / 57.102.100 libavformat 57. 76.100 / 57. 76.100 libavdevice 57. 7.100 / 57. 7.100 libavfilter 6. 95.100 / 6. 95.100 libswscale 4. 7.101 / 4. 7.101 libswresample 2. 8.100 / 2. 8.100 libpostproc 54. 6.100 / 54. 6.100 Input #0, lavfi, from 'anullsrc=r=44100': Duration: N/A, start: 0.000000, bitrate: 705 kb/s Stream #0:0: Audio: pcm_u8, 44100 Hz, stereo, u8, 705 kb/s Stream mapping: Stream #0:0 -> #0:0 (pcm_u8 (native) -> aac (native)) Press [q] to stop, [?] for help Output #0, ipod, to 'out.m4a': Metadata: encoder : Lavf57.76.100 Stream #0:0: Audio: aac (LC) (mp4a / 0x6134706D), 96000 Hz, stereo, fltp, 128 kb/s Metadata: encoder : Lavc57.102.100 aac size= 2kB time=00:00:01.00 bitrate= 13.7kbits/s speed=6.96x video:0kB audio:1kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 192.006805% [aac @ 0x7f8452003600] Qavg: 65030.441 }}} This has also been observed by a user here: https://superuser.com/questions/1218471/ -- Ticket URL: <https://trac.ffmpeg.org/ticket/6570> FFmpeg <https://ffmpeg.org> FFmpeg issue tracker
#6570: loudnorm filter changes sample rate ------------------------------------+------------------------------------ Reporter: slhck | Owner: Type: defect | Status: closed Priority: normal | Component: avfilter Version: git-master | Resolution: invalid Keywords: loudnorm | Blocked By: Blocking: | Reproduced by developer: 0 Analyzed by developer: 0 | ------------------------------------+------------------------------------ Changes (by kylophone): * status: new => closed * resolution: => invalid Comment: for true peak limiting, this filter upsamples to 192 kHz. It is up to you to downsample to an appropriate sampling rate. The rationale for this is that one may not want the same sample rate on their output stream. (why resample, resample, and then resample again?) http://k.ylo.ph/2016/04/04/loudnorm.html -- Ticket URL: <https://trac.ffmpeg.org/ticket/6570#comment:1> FFmpeg <https://ffmpeg.org> FFmpeg issue tracker
#6570: loudnorm filter changes sample rate ------------------------------------+------------------------------------ Reporter: slhck | Owner: Type: defect | Status: closed Priority: normal | Component: avfilter Version: git-master | Resolution: invalid Keywords: loudnorm | Blocked By: Blocking: | Reproduced by developer: 0 Analyzed by developer: 0 | ------------------------------------+------------------------------------ Comment (by slhck): Okay, I understand now, thanks. Of course it makes sense to avoid unnecessary resampling. But seeing that multiple users are confused by this, and that it leads to unplayable files, there should be at least a sentence in the documentation saying: “To accurately detect true peaks, the audio stream will be upsampled to 192 kHz.” One might even consider printing a warning, since no other filter that I know of will adjust the sample format or stream properties without explcitly informing the user (e.g., frame rate, pixel size, …): “Warning: Audio sample rate was automatically changed to 192 kHz.” -- Ticket URL: <https://trac.ffmpeg.org/ticket/6570#comment:2> FFmpeg <https://ffmpeg.org> FFmpeg issue tracker
#6570: Warn that loudnorm filter resamples to 192 kHz -------------------------------------+------------------------------------ Reporter: slhck | Owner: Type: enhancement | Status: reopened Priority: normal | Component: avfilter Version: git-master | Resolution: Keywords: loudnorm | Blocked By: Blocking: | Reproduced by developer: 0 Analyzed by developer: 0 | -------------------------------------+------------------------------------ Changes (by llogan): * status: closed => reopened * type: defect => enhancement * resolution: invalid => Comment: Reopening as an enhancement request. Feel free to submit a patch for the docs and/or to provide a warning. -- Ticket URL: <https://trac.ffmpeg.org/ticket/6570#comment:3> FFmpeg <https://ffmpeg.org> FFmpeg issue tracker
#6570: Warn that loudnorm filter resamples to 192 kHz -------------------------------------+------------------------------------ Reporter: slhck | Owner: Type: enhancement | Status: reopened Priority: normal | Component: avfilter Version: git-master | Resolution: Keywords: loudnorm | Blocked By: Blocking: | Reproduced by developer: 0 Analyzed by developer: 0 | -------------------------------------+------------------------------------ Comment (by slhck): Patch for the documentation submitted. Having thought about it a little more, I don't think a warning message will be appropriate, as this is normal and expected behavior of the filter. In addition, for example, warning messages for auto-selection of yuv444p for libx264 have also been removed recently. -- Ticket URL: <https://trac.ffmpeg.org/ticket/6570#comment:4> FFmpeg <https://ffmpeg.org> FFmpeg issue tracker
#6570: Warn that loudnorm filter resamples to 192 kHz -------------------------------------+------------------------------------ Reporter: slhck | Owner: Type: enhancement | Status: closed Priority: normal | Component: avfilter Version: git-master | Resolution: fixed Keywords: loudnorm | Blocked By: Blocking: | Reproduced by developer: 0 Analyzed by developer: 0 | -------------------------------------+------------------------------------ Changes (by llogan): * status: reopened => closed * resolution: => fixed Comment: Fixed by slhck in 801ba0f0ee7244f5405764c917a0b6adcbc6fb9e. -- Ticket URL: <https://trac.ffmpeg.org/ticket/6570#comment:5> FFmpeg <https://ffmpeg.org> FFmpeg issue tracker
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