ffmpeg:如何自动确定帧率? [英] ffmpeg : how to determine frame rate automatically?
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问题描述
我使用这个简单的脚本使用 ffmpeg
将视频转换为图像,但是帧频是固定的,如何自动确定呢?
I use this simple script to convert video to images using ffmpeg
, but frame rate is fixed, how can I determine it automatically?
FRAME_RATE="30"
SEPARATOR='/'
VIDEO_PATH=$1
VIDEO_BASE_DIR=`dirname $1`
FRAMES_DIR=$VIDEO_BASE_DIR$SEPARATOR"Frames"
rm -rf $FRAMES_DIR
mkdir $FRAMES_DIR
#Convert video to images
./ffmpeg -r $FRAME_RATE -i $VIDEO_PATH $FRAMES_DIR$SEPARATOR"image%d.png"
更新:
通过 ffprobe
我检查了我的第一个视频帧速率为30。
即使降低帧速率,结果也相同(产生了339帧),因此 -r
选项不起作用
By ffprobe
I checked that my 1st video frame rate is 30.
Also results are the same (339 frames are produced) even I reduce frame rate, so -r
option doesn't work or work in some other way?
这些命令给出相同的结果:
These command give the same result:
./ffmpeg -r 10 -i $VIDEO_PATH $FRAMES_DIR$SEPARATOR"image%d"$EXTENSION
./ffmpeg -r 30 -i $VIDEO_PATH $FRAMES_DIR$SEPARATOR"image%d"$EXTENSION
./ffmpeg -i $VIDEO_PATH $FRAMES_DIR$SEPARATOR"image%d"$EXTENSION
输出:
ffmpeg version N-63893-gc69defd Copyright (c) 2000-2014 the FFmpeg developers
built on Jul 16 2014 05:38:01 with gcc 4.6 (Debian 4.6.3-1)
configuration: --prefix=/root/ffmpeg-static/64bit --extra-cflags='-I/root/ffmpeg-static/64bit/include -static' --extra-ldflags='-L/root/ffmpeg-static/64bit/lib -static' --extra-libs='-lxml2 -lexpat -lfreetype' --enable-static --disable-shared --disable-ffserver --disable-doc --enable-bzlib --enable-zlib --enable-postproc --enable-runtime-cpudetect --enable-libx264 --enable-gpl --enable-libtheora --enable-libvorbis --enable-libmp3lame --enable-gray --enable-libass --enable-libfreetype --enable-libopenjpeg --enable-libspeex --enable-libvo-aacenc --enable-libvo-amrwbenc --enable-version3 --enable-libvpx
libavutil 52. 89.100 / 52. 89.100
libavcodec 55. 66.101 / 55. 66.101
libavformat 55. 43.100 / 55. 43.100
libavdevice 55. 13.101 / 55. 13.101
libavfilter 4. 8.100 / 4. 8.100
libswscale 2. 6.100 / 2. 6.100
libswresample 0. 19.100 / 0. 19.100
libpostproc 52. 3.100 / 52. 3.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/home/user/myvideo1.mp4':
Metadata:
major_brand : mp42
minor_version : 0
compatible_brands: isommp42
creation_time : 2016-01-16 05:30:03
Duration: 00:00:11.33, start: 0.000000, bitrate: 4659 kb/s
Stream #0:0(eng): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 640x480, 4539 kb/s, SAR 65536:65536 DAR 4:3, 30 fps, 30 tbr, 90k tbn, 180k tbc (default)
Metadata:
rotate : 90
creation_time : 2016-01-16 05:30:03
handler_name : VideoHandle
Stream #0:1(eng): Audio: aac (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 127 kb/s (default)
Metadata:
creation_time : 2016-01-16 05:30:03
handler_name : SoundHandle
Output #0, image2, to '/home/user/Frames/image%d.png':
Metadata:
major_brand : mp42
minor_version : 0
compatible_brands: isommp42
encoder : Lavf55.43.100
Stream #0:0(eng): Video: png, rgb24, 640x480 [SAR 1:1 DAR 4:3], q=2-31, 200 kb/s, 30 fps, 90k tbn, 30 tbc (default)
Metadata:
rotate : 90
creation_time : 2016-01-12 05:38:03
handler_name : VideoHandle
encoder : Lavc55.66.101 png
Stream mapping:
Stream #0:0 -> #0:0 (h264 (native) -> png (png))
Press [q] to stop, [?] for help
frame= 339 fps= 68 q=0.0 Lsize=N/A time=00:00:11.30 bitrate=N/A
video:195852kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown
推荐答案
ffprobe -v 0 -of compact=p=0 -select_streams 0 \
-show_entries stream=r_frame_rate 'The Master (2012).mp4'
结果:
r_frame_rate=24000/1001
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