[FFmpeg-trac] #2759(undetermined:closed): Audio equalizer filter problem - clipping with negative gain
FFmpeg
trac at avcodec.org
Sun Jul 7 18:46:10 CEST 2013
#2759: Audio equalizer filter problem - clipping with negative gain
-------------------------------------+-------------------------------------
Reporter: Ajaja | Owner:
Type: defect | Status: closed
Priority: normal | Component:
Version: git-master | undetermined
Keywords: | Resolution: invalid
Blocking: | Blocked By:
Analyzed by developer: 0 | Reproduced by developer: 0
-------------------------------------+-------------------------------------
Comment (by Ajaja):
Yes, it not normalaized (-0.989990...0.989990). But problem is not in
source. With +0.1dB gain there is no any messages:
{{{
% ffmpeg -i noise.wav -af equalizer=2000:q:1:0.1 noise3.wav
...
Guessed Channel Layout for Input Stream #0.0 : mono
Input #0, wav, from 'noise.wav':
Metadata:
encoder : Lavf55.11.100
Duration: 00:01:00.00, bitrate: 705 kb/s
Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 44100 Hz, mono,
s16, 705 kb/s
Output #0, wav, to 'noise2.wav':
Metadata:
ISFT : Lavf55.11.100
Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 44100 Hz, mono,
s16, 705 kb/s
Stream mapping:
Stream #0:0 -> #0:0 (pcm_s16le -> pcm_s16le)
Press [q] to stop, [?] for help
size= 5168kB time=00:01:00.00 bitrate= 705.6kbits/s
video:0kB audio:5168kB subtitle:0 global headers:0kB muxing overhead
0.001512%
}}}
Stats after +0.1dB:
{{{
% ffmpeg -i noise3.wav -filter:a "astats" -vn -f null NUL
...
[Parsed_astats_0 @ 00000000026486c0] Overall
[Parsed_astats_0 @ 00000000026486c0] DC offset: 0.000367
[Parsed_astats_0 @ 00000000026486c0] Min level: -0.997406
[Parsed_astats_0 @ 00000000026486c0] Max level: 0.997650
}}}
All OK. It's -0.997406..0.997650 now, little gain and no clipping
messages.
Let's test normilized sourse:
{{{
% sox noise.wav noise4.wav norm
...
% ffmpeg -i noise4.wav -filter:a "astats" -vn -f null NUL
...
[Parsed_astats_0 @ 00000000024e86c0] Overall
[Parsed_astats_0 @ 00000000024e86c0] DC offset: 0.000371
[Parsed_astats_0 @ 00000000024e86c0] Min level: -1.000000
[Parsed_astats_0 @ 00000000024e86c0] Max level: 0.999969
% ffmpeg -i noise4.wav -af equalizer=2000:q:1:-5 -y noise5.wav
....
Guessed Channel Layout for Input Stream #0.0 : mono
Input #0, wav, from 'noise4.wav':
Duration: 00:01:00.00, bitrate: 705 kb/s
Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 44100 Hz, mono,
s16, 705 kb/s
Output #0, wav, to 'noise5.wav':
Metadata:
ISFT : Lavf55.11.100
Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 44100 Hz, mono,
s16, 705 kb/s
Stream mapping:
Stream #0:0 -> #0:0 (pcm_s16le -> pcm_s16le)
Press [q] to stop, [?] for help
clipping
Last message repeated 679 times
clipping 100kB time=00:00:01.16 bitrate= 706.2kbits/s
Last message repeated 643 times
clipping 196kB time=00:00:02.27 bitrate= 705.9kbits/s
Last message repeated 651 times
....
}}}
clipping again.
--
Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/2759#comment:5>
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