[FFmpeg-user] af_silenceremove timestamp copy option doesn't seem to work
Bouke / Videotoolshed
bouke at videotoolshed.com
Sat Jan 25 21:43:11 EET 2025
> On 25 Jan 2025, at 20:36, Phil Rhodes via ffmpeg-user <ffmpeg-user at ffmpeg.org> wrote:
>
> Define "timestamps" in this context?
I think he’s referring to the BWF samples after midnight, either in the Bext or iXML chunk.
Bouke
videotoolshed.com
Van Oldenbarneveltstraat 33
6512 AS Nijmegen, the Netherlands
+31 6 21817248
If you want to send me large files, please use:
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> I've seen wave files that can store various types of marker.
> P
> On Saturday 25 January 2025 at 09:37:39 GMT, Paul B Mahol <onemda at gmail.com> wrote:
>
> wav format container does not store timestamps at all.
> Filter works fine.
>
> On Sat, Jan 25, 2025 at 4:42 AM Justin <justinrsilver at gmail.com> wrote:
>
>> Hello!
>>
>> I am trying to use the *silenceremove *filter as explained in the ffmpeg
>> documentation. <https://ffmpeg.org/ffmpeg-filters.html#toc-silenceremove>
>> I
>> wanted to keep the original timestamps from the modified audio file with
>> the *timestamp=copy *option. The silence is removed as expected, but after
>> running *ashowinfo*, the original timestamps seem to have been modified. In
>> fact, regardless of *timestamp=copy *and *timestamp=write*, there is no
>> difference in the *pts* output values. I might be misunderstanding how it
>> works though, so I wanted to double check here.
>>
>> Here is what I did.
>>
>> 1. Downloaded a sample sound with multiple silences. This is the sound
>> <https://freesound.org/people/frosthardr/sounds/253067/> I used. I
>> named
>> it *in.wav*. If you take a look at the waveform, there are 4 pulses of
>> sound that last roughly 2.5 seconds, with about 1 second of silence
>> between
>> each one (the entire audio clip is roughly 15 seconds).
>>
>> 2. I used the following command to generate an output with copied
>> timestamps:
>>
>> *Command:*
>> *ffmpeg -y -i ~/files/test_ffmpeg/in.wav -filter_complex
>> silenceremove=stop_periods=-1:timestamp=copy:stop_threshold=-30dB
>> ~/files/test_ffmpeg/out_copy.wav*
>>
>> * Output:*
>>
>>
>>
>>
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>>
>> *ffmpeg version N-118350-ge20ee9f9ae Copyright (c) 2000-2025 the FFmpeg
>> developers built with gcc 11 (Ubuntu 11.4.0-1ubuntu1~22.04)
>> configuration: --prefix=/home/justin/ffmpeg_build
>> --pkg-config-flags=--static
>> --extra-cflags=-I/home/justin/ffmpeg_build/include
>> --extra-ldflags=-L/home/justin/ffmpeg_build/lib --extra-libs='-lpthread
>> -lm' --ld=g++ --bindir=/home/justin/bin --enable-gpl --enable-gnutls
>> --enable-libfdk-aac --enable-libmp3lame --enable-libopus
>> --enable-nonfree
>> libavutil 59. 55.100 / 59. 55.100 libavcodec 61. 31.101 / 61.
>> 31.101 libavformat 61. 9.106 / 61. 9.106 libavdevice 61.
>> 4.100
>> / 61. 4.100 libavfilter 10. 6.101 / 10. 6.101 libswscale
>> 8.
>> 13.100 / 8. 13.100 libswresample 5. 4.100 / 5. 4.100
>> libpostproc
>> 58. 4.100 / 58. 4.100 [aist#0:0/pcm_s16le @ 0x5621b0ab7a40] Guessed
>> Channel Layout: stereo Input #0, wav, from
>> '/home/justin/files/test_ffmpeg/in.wav': Metadata: title
>> :
>> Electronic Drum Loop 01 artist : Matech comment
>> :
>> soundcloud.com/matech-1/ <http://soundcloud.com/matech-1/> Duration:
>> 00:00:15.24, bitrate: 1411 kb/s Stream #0:0: Audio: pcm_s16le
>> ([1][0][0][0] / 0x0001), 44100 Hz, stereo, s16, 1411 kb/s Stream
>> mapping:
>> Stream #0:0 (pcm_s16le) -> silenceremove:default
>> silenceremove:default ->
>> Stream #0:0 (pcm_s16le) Press [q] to stop, [?] for help Output #0, wav,
>> to
>> '/home/justin/files/test_ffmpeg/out_copy.wav': Metadata: INAM
>> : Electronic Drum Loop 01 IART : Matech ICMT
>> : soundcloud.com/matech-1/ <http://soundcloud.com/matech-1/>
>> ISFT
>> : Lavf61.9.106 Stream #0:0: Audio: pcm_s16le ([1][0][0][0] /
>> 0x0001), 44100 Hz, stereo, s16, 1411 kb/s Metadata: encoder
>> : Lavc61.31.101 pcm_s16le [out#0/wav @ 0x5621b0ab9e00] video:0KiB
>> audio:1110KiB subtitle:0KiB other streams:0KiB global headers:0KiB
>> muxing
>> overhead: 0.014075% size= 1110KiB time=00:00:13.28 bitrate=
>> 684.7kbits/s
>> speed= 459x *
>>
>> 3. I also generated an output with overwritten timestamps:
>>
>> *Command:*
>> *ffmpeg -y -i ~/files/test_ffmpeg/in.wav -filter_complex
>> silenceremove=stop_periods=-1:timestamp=write:stop_threshold=-30dB
>> ~/files/test_ffmpeg/out_write.wav*
>>
>> *Output:*
>>
>>
>>
>>
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>>
>>
>>
>>
>> *ffmpeg version N-118350-ge20ee9f9ae Copyright (c) 2000-2025 the FFmpeg
>> developers built with gcc 11 (Ubuntu 11.4.0-1ubuntu1~22.04)
>> configuration: --prefix=/home/justin/ffmpeg_build
>> --pkg-config-flags=--static
>> --extra-cflags=-I/home/justin/ffmpeg_build/include
>> --extra-ldflags=-L/home/justin/ffmpeg_build/lib --extra-libs='-lpthread
>> -lm' --ld=g++ --bindir=/home/justin/bin --enable-gpl --enable-gnutls
>> --enable-libfdk-aac --enable-libmp3lame --enable-libopus
>> --enable-nonfree
>> libavutil 59. 55.100 / 59. 55.100 libavcodec 61. 31.101 / 61.
>> 31.101 libavformat 61. 9.106 / 61. 9.106 libavdevice 61.
>> 4.100
>> / 61. 4.100 libavfilter 10. 6.101 / 10. 6.101 libswscale
>> 8.
>> 13.100 / 8. 13.100 libswresample 5. 4.100 / 5. 4.100
>> libpostproc
>> 58. 4.100 / 58. 4.100 [aist#0:0/pcm_s16le @ 0x5c514279ea40] Guessed
>> Channel Layout: stereo Input #0, wav, from
>> '/home/justin/files/test_ffmpeg/in.wav': Metadata: title
>> :
>> Electronic Drum Loop 01 artist : Matech comment
>> :
>> soundcloud.com/matech-1/ <http://soundcloud.com/matech-1/> Duration:
>> 00:00:15.24, bitrate: 1411 kb/s Stream #0:0: Audio: pcm_s16le
>> ([1][0][0][0] / 0x0001), 44100 Hz, stereo, s16, 1411 kb/s Stream
>> mapping:
>> Stream #0:0 (pcm_s16le) -> silenceremove:default
>> silenceremove:default ->
>> Stream #0:0 (pcm_s16le) Press [q] to stop, [?] for help Output #0, wav,
>> to
>> '/home/justin/files/test_ffmpeg/out_write.wav': Metadata: INAM
>> : Electronic Drum Loop 01 IART : Matech ICMT
>> : soundcloud.com/matech-1/ <http://soundcloud.com/matech-1/>
>> ISFT
>> : Lavf61.9.106 Stream #0:0: Audio: pcm_s16le ([1][0][0][0]
>> /
>> 0x0001), 44100 Hz, stereo, s16, 1411 kb/s Metadata: encoder
>> : Lavc61.31.101 pcm_s16le [out#0/wav @ 0x5c51427a0e00] video:0KiB
>> audio:1110KiB subtitle:0KiB other streams:0KiB global headers:0KiB
>> muxing
>> overhead: 0.014075% size= 1110KiB time=00:00:06.44
>> bitrate=1411.4kbits/s
>> speed= 227x *
>>
>> 4. I then ran the following commands to get the timestamp output for
>> each of the above files. See the attached files since the output was too
>> long to paste here.
>>
>> *ffmpeg -i ~/files/test_ffmpeg/in.wav -filter_complex ashowinfo -f null
>> - 2> ~/files/test_ffmpeg/in_ashowinfo.txt*
>> *ffmpeg -i ~/files/test_ffmpeg/out_copy.wav -filter_complex ashowinfo -f
>> null - 2> ~/files/test_ffmpeg/out_copy_ashowinfo.txt*
>> *ffmpeg -i ~/files/test_ffmpeg/out_write.wav -filter_complex ashowinfo
>> -f null - 2> ~/files/test_ffmpeg/out_write_ashowinfo.txt*
>>
>> Here are the ends of the files to explain the issue:
>>
>> *in_ashowinfo.txt *
>>
>>
>>
>>
>>
>>
>> *[Parsed_ashowinfo_0 @ 0x72aa280025c0] n:160 pts:655360 pts_time:14.860771
>> fmt:s16 channels:2 chlayout:stereo rate:44100 nb_samples:4096
>> checksum:BFC63EA4 plane_checksums: [ BFC63EA4 ][Parsed_ashowinfo_0 @
>> 0x72aa280025c0] n:161 pts:659456 pts_time:14.953651 fmt:s16 channels:2
>> chlayout:stereo rate:44100 nb_samples:4096 checksum:44D92A6E
>> plane_checksums: [ 44D92A6E ][Parsed_ashowinfo_0 @ 0x72aa280025c0] n:162
>> pts:663552 pts_time:15.046531 fmt:s16 channels:2 chlayout:stereo rate:44100
>> nb_samples:4096 checksum:071FC31C plane_checksums: [ 071FC31C
>> ][Parsed_ashowinfo_0 @ 0x72aa280025c0] n:163 pts:667648 pts_time:15.13941
>> fmt:s16 channels:2 chlayout:stereo rate:44100 nb_samples:4096
>> checksum:AD15BC98 plane_checksums: [ AD15BC98 ][Parsed_ashowinfo_0 @
>> 0x72aa280025c0] n:164 pts:671744 pts_time:15.23229 fmt:s16 channels:2
>> chlayout:stereo rate:44100 nb_samples:256 checksum:00000000
>> plane_checksums: [ 00000000 ][out#0/null @ 0x5a0bc0b35440] video:0KiB
>> audio:2625KiB subtitle:0KiB other streams:0KiB global headers:0KiB muxing
>> overhead: unknownsize=N/A time=00:00:15.23 bitrate=N/A speed=1.81e+03x *
>>
>>
>> *out_copy_ashowinfo.txt *
>>
>>
>>
>>
>>
>>
>>
>> *[Parsed_ashowinfo_0 @ 0x7fc9fc0025c0] n:64 pts:262144 pts_time:5.944308
>> fmt:s16 channels:2 chlayout:stereo rate:44100 nb_samples:4096
>> checksum:340B4DDC plane_checksums: [ 340B4DDC ][Parsed_ashowinfo_0 @
>> 0x7fc9fc0025c0] n:65 pts:266240 pts_time:6.037188 fmt:s16 channels:2
>> chlayout:stereo rate:44100 nb_samples:4096 checksum:F2148934
>> plane_checksums: [ F2148934 ][Parsed_ashowinfo_0 @ 0x7fc9fc0025c0] n:66
>> pts:270336 pts_time:6.130068 fmt:s16 channels:2 chlayout:stereo rate:44100
>> nb_samples:4096 checksum:F374BB67 plane_checksums: [ F374BB67
>> ][Parsed_ashowinfo_0 @ 0x7fc9fc0025c0] n:67 pts:274432 pts_time:6.222948
>> fmt:s16 channels:2 chlayout:stereo rate:44100 nb_samples:4096
>> checksum:570F8385 plane_checksums: [ 570F8385 ][Parsed_ashowinfo_0 @
>> 0x7fc9fc0025c0] n:68 pts:278528 pts_time:6.315828 fmt:s16 channels:2
>> chlayout:stereo rate:44100 nb_samples:4096 checksum:0983C2F7
>> plane_checksums: [ 0983C2F7 ][Parsed_ashowinfo_0 @ 0x7fc9fc0025c0] n:69
>> pts:282624 pts_time:6.408707 fmt:s16 channels:2 chlayout:stereo rate:44100
>> nb_samples:1560 checksum:017E3AB0 plane_checksums: [ 017E3AB0 ][out#0/null
>> @ 0x61dc2756bac0] video:0KiB audio:1110KiB subtitle:0KiB other streams:0KiB
>> global headers:0KiB muxing overhead: unknownsize=N/A time=00:00:06.44
>> bitrate=N/A speed=1.99e+03x *
>>
>> Based on the waveform, the *out_copy_ashowinfo.txt *says the last
>> timestamp is roughly 6 seconds, but if the original timestamps were
>> maintained then it should be roughly 11 seconds, since this is when the
>> last pulse of audio is played. I would expect there to be gaps in the
>> timestamps which correspond to the removed silence but there isn't. Also
>> note that the contents of *out_write_ashowinfo.txt *is identical to
>> *out_copy_ashowinfo.txt*, so the option doesn't seem to do anything.
>>
>> Thanks all for your help!
>> -Justin
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