问题描述
我正在测试ffmpeg中的"blackdetect"过滤器.我想有一段视频是黑色的，可以通过脚本(例如动作脚本或javascript)读取.我试过了:
I'm testing out the "blackdetect" filter in ffmpeg. I want to have the times when the video is black to be read by a script (like actionscript or javascript). I tried:
ffmpeg -i video1.mp4 -vf "blackdetect=d=2:pix_th=0.00" -an -f null -
在ffmpeg日志中，我得到了一个不错的结果:
And I get a nice result in the ffmpeg log:
ffmpeg version N-55644-g68b63a3 Copyright (c) 2000-2013 the FFmpeg developers
built on Aug 19 2013 20:32:00 with gcc 4.7.3 (GCC)
configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-av
isynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enab
le-iconv --enable-libass --enable-libbluray --enable-libcaca --enable-libfreetyp
e --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame --ena
ble-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-l
ibopus --enable-librtmp --enable-libschroedinger --enable-libsoxr --enable-libsp
eex --enable-libtheora --enable-libtwolame --enable-libvo-aacenc --enable-libvo-
amrwbenc --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libxavs --
enable-libxvid --enable-zlib
libavutil 52. 42.100 / 52. 42.100
libavcodec 55. 28.100 / 55. 28.100
libavformat 55. 13.103 / 55. 13.103
libavdevice 55. 3.100 / 55. 3.100
libavfilter 3. 82.100 / 3. 82.100
libswscale 2. 5.100 / 2. 5.100
libswresample 0. 17.103 / 0. 17.103
libpostproc 52. 3.100 / 52. 3.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'video1.mp4':
Metadata:
major_brand : isom
minor_version : 512
compatible_brands: isomiso2avc1mp41
creation_time : 1970-01-01 00:00:00
encoder : Lavf53.13.0
Duration: 00:02:01.54, start: 0.000000, bitrate: 275 kb/s
Stream #0:0(eng): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 768x432 [
SAR 1:1 DAR 16:9], 211 kb/s, 25 fps, 25 tbr, 25 tbn, 50 tbc
Metadata:
creation_time : 1970-01-01 00:00:00
handler_name : VideoHandler
Stream #0:1(eng): Audio: aac (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 59
kb/s
Metadata:
creation_time : 1970-01-01 00:00:00
handler_name : SoundHandler
Output #0, null, to 'pipe:':
Metadata:
major_brand : isom
minor_version : 512
compatible_brands: isomiso2avc1mp41
encoder : Lavf55.13.103
Stream #0:0(eng): Video: rawvideo (I420 / 0x30323449), yuv420p, 768x432 [SAR
1:1 DAR 16:9], q=2-31, 200 kb/s, 90k tbn, 25 tbc
Metadata:
creation_time : 1970-01-01 00:00:00
handler_name : VideoHandler
Stream mapping:
Stream #0:0 -> #0:0 (h264 -> rawvideo)
Press [q] to stop, [?] for help
[null @ 00000000003279a0] Encoder did not produce proper pts, making some up.
[blackdetect @ 0000000004d5e800] black_start:0 black_end:17.08 black_duration:17
.08
[blackdetect @ 0000000004d5e800] black_start:62.32 black_end:121.48 black_durati
on:59.16
frame= 3038 fps=2317 q=0.0 Lsize=N/A time=00:02:01.52 bitrate=N/A
video:285kB audio:0kB subtitle:0 global headers:0kB muxing overhead -100.007543%
我对这部分特别感兴趣:
And I'm particularly interested in this part:
[blackdetect @ 0000000004e2e340] black_start:0 black_end:17.08 black_duration:17.08
[blackdetect @ 0000000004e2e340] black_start:62.32 black_end:121.48 black_duration:59.16
所以我的问题:
- 有没有办法只将blackdetect过滤器的输出放到.txt文件中?
- 如果可能的话，有没有一种方法可以在具有多个视频输入的语句中执行此操作?就像在这个例子中一样
示例:
example:
ffmpeg -f concat -i mylist.txt -c copy concat.mp4
mylist.txt是视频列表:
Where mylist.txt is a list of videos:
file 'video1.mp4'
file 'video2.mp4'
file 'video3.mp4'
file 'video4.mp4'
我基本上想要的是一个或多个文本文件，其中包含有关此列表中每个视频中黑框的信息，供其他程序使用
Basically what I want to have is one or more text files containing information about the black frames in every video in this list to be used by another program
推荐答案
默认情况下，ffmpeg记录到stderr.您可以输出到stdout，然后使用grep隔离 blackdetect 行:
By default ffmpeg logs to stderr. You can output to stdout and then use grep to isolate the blackdetect lines:
$ ffmpeg -i video1.mp4 -vf "blackdetect=d=2:pix_th=0.00" -an -f null - 2>&1 | grep blackdetect > output.txt
结果:
$ cat output.txt
[blackdetect @ 0x1d2b980] black_start:5.16 black_end:10.24 black_duration:5.08
如果要附加到output.txt而不是为每个实例覆盖，请使用>>而不是>，例如:blackdetect >> output.txt.
If you want to append to output.txt instead of overwriting for each instance then use >> instead of >, as in: blackdetect >> output.txt.
您可以将blackdetect与 concat多路分解器结合使用，但是您的问题所示请注意，black_start和black_end时间将是累积时间，而不是独立于每个输入，因为您正在串联所有输入.
You can use blackdetect with the concat demuxer as shown in your question, but be aware that the black_start and black_end times will be cumulative, and not independent to each input, because you are concatenating all inputs.
或者，如果您希望每个输入都通过blackdetect独立运行，则可以使用bash"for循环":
Alternatively you can use a bash "for loop" if you want each input to be independently run through blackdetect:
for f in *.mp4; do ffmpeg -i "$f" -vf "blackdetect=d=2:pix_th=0.00" -an -f null - 2>&1 | grep blackdetect > "$f".txt; done
这可能会创建空的txt文件.
This may create empty txt files.
这篇关于您可以使用ffmpeg将blackdetect过滤器的结果放入文本文件中吗?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！