目录
1. FFmpeg滤镜文档
2. 示例
2.1 缩放
2.2 视频加速
2.3 滤镜图，链和滤镜关系
2.4 多个输入覆盖同一个2x2 网格
2.5 转义字符
2.6 烧录时间码
2.7 描述命令行参数
2.8 测试源
3. 滤镜列表
4. 其它滤镜示例
5. 开发自己的滤镜
FFmpeg添加了很多滤镜，查看哪些滤镜有效可用命令:
# ./ffmpeg -filters.
1. FFmpeg滤镜文档
更多的信息和每个滤镜的使用示例可查看FFmpeg的滤镜文档:
http://ffmpeg.org/ffmpeg-filters.html
2. 示例
2.1 缩放
将输入的640x480缩小到320x240输出:
# ./ffmpeg -i input -vf scale=iw/2:-1 output
iw : 是输入的宽度；在本例中，输入宽度为640. 640/2 = 320.
-1 : 通知缩放滤镜在输出时保持原始的宽高比，因此本例中缩放滤镜将选择240.
2.2 视频加速
1. 加速/减慢视频
可以使用 “setpts"（http://ffmpeg.org/ffmpeg.html#asetpts_002c-setpts）滤镜来改变视频速度。
加速视频命令:
# ./ffmpeg -i input.mkv -filter:v "setpts=0.5*PTS" output.mkv
Note : 这个方法在实现你想要的速度时，会采取丢帧策略。
如果想避免丢帧，可以指定输出的帧率比输入的帧率高的办法。
例如，输入的帧率为4， 指定输出的帧率为4x, 即16fps :
# ./ffmpeg -i input.mkv -r 16 -filter:v "setpts=0.125*PTS" -an output.mkv
减慢视频命令:
# ./ffmpeg -i input.mkv -filter:v "setpts=2.0*PTS" output.mkv
2. 加速/减慢音频
可以使用" atempo" 音频滤镜来加速或减慢音频。如双倍速音频命令:
# ./ffmpeg -i input.mkv -filter:a "atempo=2.0" -vn output.mkv
"atempo"滤镜对音频速度调整限制在0.5 到 2.0 之间，（即半速或倍速）。
如果有必要，可以使用多个atempo滤镜来实现,如下面的命令实现四倍速音频:
# ./ffmpeg -i input.mkv -filter:a "atempo=2.0,atempo=2.0" -vn output.mkv
使用更复杂的滤镜图，可以同时加速视频和音频：
# ./ffmpeg -i input.mkv -filter_complex "[0:v]setpts=0.5*PTS[v];[0:a]atempo=2.0[a]" -map "[v]" -map "[a]" output.mkv
2.3 滤镜图，链，和滤镜关系
FFmpeg命令行中，跟在 "-vf"之后的就是一个滤镜图。
滤镜图可以包含多个滤镜链，而每个滤镜链又可以包含多个滤镜。
虽然一个完整的滤镜图描述很复杂，但可以简化以避免歧义。
滤镜链使用";"分隔，滤镜链中滤镜使用","分隔；
并且，滤镜链如果没有指定输入或输出，则默认使用前面的滤镜链的输出为输入，并输出给后面的滤镜链做输入。
下面的命令行是相等的:
ffmpeg -i input -vf [in]scale=iw/2:-1[out] output
ffmpeg -i input -vf scale=iw/2:-1 output # the input and output are implied without ambiguity
对于下面:
ffmpeg -i input -vf [in]yadif=0:0:0[middle];[middle]scale=iw/2:-1[out] output
# 两个链的方式，每个链一个滤镜，链间使用[middle]填充
ffmpeg -i input -vf [in]yadif=0:0:0,scale=iw/2:-1[out] output
# 一个链的方式，链包含两个滤镜，使用默认链接
ffmpeg -i input -vf yadif=0:0:0,scale=iw/2:-1 output # 输入输出也使用默认链接
2.4. 多个输入覆盖同一个2x2网格
下例中有四个输入，并使用 -filter_complex滤镜链接。
这个例子中四个输入都是 "-f lavfi -i testsrc", 也可以用别的输入代替。
在滤镜图中，第一个输入被填充到右下角，并设置成高度的两倍。
其它三个输入使用独立的滤镜"hflip, negate,和 edgedetect"。
覆盖视频滤镜被使用多次，后面三个都覆盖到第一个之上。
覆盖滤镜的偏移量在输入上形成一个网格。
# ./ffmpeg -f lavfi -i testsrc -f lavfi -i testsrc -f lavfi -i testsrc -f lavfi -i testsrc
-filter_complex "[0:0]pad=iw*2:ih*2[a];[1:0]negate[b];[2:0]hflip[c];
[3:0]edgedetect[d];[a][b]overlay=w[x];[x][c]overlay=0:h[y];[y][d]overlay=w:h"
-y -c:v ffv1 -t 5 multiple_input_grid.avi
2.5 转义字符
如文档中的描述，滤镜间的"，"分隔符是必须的，但它也会出现在参数中，如下面的"select"滤镜:
# ./ffmpeg -i input -vf select='eq(pict_type\,PICT_TYPE_I)' output
# to select only I frames
作为一个选择，在滤镜图中同样可以在双引号中使用空格，这样更方便阅读:
# ./ffmpeg -i input -vf "select=eq(pict_type,PICT_TYPE_I)" output # to select only I frames
# ./ffmpeg -i input -vf "yadif=0:-1:0, scale=iw/2:-1" output # deinterlace then resize
2.6 烧录时间码
使用 "drawtext"视频滤镜。
PAL 25 fps non drop frame:
ffmpeg -i in.mp4 -vf "drawtext=fontfile=/usr/share/fonts/truetype/DroidSans.ttf: timecode='09\:57\:00\:00': r=25: \
x=(w-tw)/2: y=h-(2*lh): fontcolor=white: box=1: boxcolor=0x00000000@1" -an -y out.mp4
NTSC 30 fps drop frame
(change the : to a ; before the frame count)_________________________________________________________
\
ffmpeg -i in.mp4 -vf "drawtext=fontfile=/usr/share/fonts/truetype/DroidSans.ttf: timecode='09\:57\:00\;00': r=30: \
x=(w-tw)/2: y=h-(2*lh): fontcolor=white: box=1: boxcolor=0x00000000@1" -an -y out.mp4
2.7 描述命令行参数
构建复杂的滤镜图时，会使命令行看起来一团混乱，如何使滤镜图命令行可管理就变得很有用了。
下面的例子包含三个滤镜，yadif, scale, drawtext的滤镜图的脚本:
#!/bin/bash
# ffmpeg test script
path="/path/to/file/"
in_file="in.mp4"
out_file="out.mp4"
cd $path
filter="-vf \"yadif=0:-1:0, scale=400:226, drawtext=fontfile=/usr/share/fonts/truetype/DroidSans.ttf: \
text='tod- %X':x=(w-text_w)/2:y=H-60 :fontcolor=white :box=1:boxcolor=0x00000000@1\""
codec="-vcodec libx264 -pix_fmt yuv420p -b:v 700k -r 25 -maxrate 700k -bufsize 5097k"
command_line="ffmpeg -i $in_file $filter $codec -an $out_file"
echo $command_line
eval $command_line
exit
NOTE: 包含整个滤镜图的双引号需要使用转义符 \",
eval $command_line变量用于避免转义符丢失。
2.8 测试源
testsrc源滤镜生成一个测试视频源，包含有颜色模式，灰度值和时间戳。它在用于测试目的时很有用。
下面的例子生成一个10秒的输出，30fps,共300帧，帧大小为 1280x720:
# ./ffmpeg -f lavfi -i testsrc=duration=10:size=1280x720:rate=30 output.mpg
使用 smptebars源滤镜的例子:
# ./ffmpeg -f lavfi -i "smptebars=duration=5:size=1280x720:rate=30" output.mp4
ffplay同样能用于查看结果滤镜图:
ffplay -f lavfi -i "testsrc=duration=10:size=1280x720:rate=30"
3. 滤镜列表
滤镜和libavfilter绑定在一起，如 4.3.100(as configured with --enable-gpl).
使用外部库的滤镜并未列在这里，如frei0r.可以查看FFMPEG的滤镜文档。
滤镜列表约定:
T.. = Timeline support
.S. = Slice threading
..C = Commmand support
A = Audio input/output
V = Video input/output
N = Dynamic number and/or type of input/output
| = Source or sink filter
滤镜:
... aconvert A->A Convert the input audio to sample_fmt:channel_layout.
T.. adelay A->A 延迟一个或多个音频通道
... aecho A->A 给音频添加回音
... aeval A->A Filter audio signal according to a specified expression.
T.. afade A->A Fade in/out input audio.
... aformat A->A Convert the input audio to one of the specified formats.
... ainterleave N->A Temporally interleave audio inputs.
... allpass A->A Apply a two-pole all-pass filter.
... amerge N->A Merge two or more audio streams into a single multi-channel stream.
... amix N->A Audio mixing.
... anull A->A Pass the source unchanged to the output.
T.. apad A->A Pad audio with silence.
... aperms A->A Set permissions for the output audio frame.
... aphaser A->A Add a phasing effect to the audio.
... aresample A->A 重采样音频数据
... aselect A->N 选择音频帧给输出
... asendcmd A->A Send commands to filters.
... asetnsamples A->A Set the number of samples for each output audio frames.
... asetpts A->A Set PTS for the output audio frame.
... asetrate A->A Change the sample rate without altering the data.
... asettb A->A Set timebase for the audio output link.
... ashowinfo A->A Show textual information for each audio frame.
... asplit A->N Pass on the audio input to N audio outputs.
... astats A->A Show time domain statistics about audio frames.
... astreamsync AA->AA Copy two streams of audio data in a configurable order.
..C atempo A->A Adjust audio tempo.
... atrim A->A Pick one continuous section from the input, drop the rest.
... bandpass A->A Apply a two-pole Butterworth band-pass filter.
... bandreject A->A Apply a two-pole Butterworth band-reject filter.
... bass A->A Boost or cut lower frequencies.
... biquad A->A Apply a biquad IIR filter with the given coefficients.
... channelmap A->A Remap audio channels.
... channelsplit A->N Split audio into per-channel streams.
... compand A->A Compress or expand audio dynamic range.
... earwax A->A Widen the stereo image.
... ebur128 A->N EBU R128 scanner.
... equalizer A->A Apply two-pole peaking equalization (EQ) filter.
... highpass A->A Apply a high-pass filter with 3dB point frequency.
... join N->A Join multiple audio streams into multi-channel output.
... lowpass A->A Apply a low-pass filter with 3dB point frequency.
... pan A->A Remix channels with coefficients (panning).
... replaygain A->A ReplayGain scanner.
... silencedetect A->A 检测静音
... treble A->A Boost or cut upper frequencies.
T.C volume A->A 改变输入音量
... volumedetect A->A 检测音频音量
... aevalsrc |->A Generate an audio signal generated by an expression.
... anullsrc |->A Null audio source, return empty audio frames.
... sine |->A Generate sine wave audio signal.
... anullsink A->| Do absolutely nothing with the input audio.
... alphaextract V->N Extract an alpha channel as a grayscale image component.
... alphamerge VV->V Copy the luma value of the second input into the alpha channel of the first input.
T.. bbox V->V Compute bounding box for each frame.
... blackdetect V->V Detect video intervals that are (almost) black.
... blackframe V->V 检测几乎全黑的帧
TS. blend VV->V Blend two video frames into each other.
T.. boxblur V->V Blur the input.
T.. colorbalance V->V Adjust the color balance.
T.. colorchannelmixer V->V Adjust colors by mixing color channels.
T.. colormatrix V->V Convert color matrix.
... copy V->V 复制输入视频到输出
... crop V->V 裁剪输入视频
T.. cropdetect V->V 自动检测裁剪尺寸
TS. curves V->V Adjust components curves.
T.. dctdnoiz V->V Denoise frames using 2D DCT.
... decimate N->V Decimate frames (post field matching filter).
... dejudder V->V Remove judder produced by pullup.
T.. delogo V->V 去掉输入视频的logo
... deshake V->V Stabilize shaky video.
T.. drawbox V->V 在输入视频上画一个颜色块
T.. drawgrid V->V 在输入视频上画一个颜色网格
T.. edgedetect V->V 检测并画边缘
... elbg V->V Apply posterize effect, using the ELBG algorithm.
... extractplanes V->N Extract planes as grayscale frames.
.S. fade V->V Fade in/out input video.
... field V->V Extract a field from the input video.
... fieldmatch N->V Field matching for inverse telecine.
T.. fieldorder V->V Set the field order.
... format V->V Convert the input video to one of the specified pixel formats.
... fps V->V 强制成常量帧率Force constant framerate.
... framepack VV->V Generate a frame packed stereoscopic video.
T.. framestep V->V 每N帧中选择一帧
T.. geq V->V Apply generic equation to each pixel.
T.. gradfun V->V Debands video quickly using gradients.
TS. haldclut VV->V Adjust colors using a Hald CLUT.
.S. hflip V->V Horizontally flip the input video.
T.. histeq V->V Apply global color histogram equalization.
... histogram V->V 计算并画直方图
T.. hqdn3d V->V Apply a High Quality 3D Denoiser.
T.C hue V->V Adjust the hue and saturation of the input video.
... idet V->V 隔行检测滤镜
T.. il V->V 去隔行或隔行场
... interlace V->V 转换逐行视频成隔行视频
... interleave N->V Temporally interleave video inputs.
... kerndeint V->V Apply kernel deinterlacing to the input.
TS. lut3d V->V Adjust colors using a 3D LUT.
T.. lut V->V Compute and apply a lookup table to the RGB/YUV input video.
T.. lutrgb V->V Compute and apply a lookup table to the RGB input video.
T.. lutyuv V->V Compute and apply a lookup table to the YUV input video.
... mcdeint V->V Apply motion compensating deinterlacing.
... mergeplanes N->V Merge planes.
... mp V->V Apply a libmpcodecs filter to the input video.
... mpdecimate V->V Remove near-duplicate frames.
T.. negate V->V Negate input video.
... noformat V->V Force libavfilter not to use any of the specified pixel formats for the input to the next filter.
TS. noise V->V Add noise.
... null V->V Pass the source unchanged to the output.
T.C overlay VV->V Overlay a video source on top of the input.
T.. owdenoise V->V Denoise using wavelets.
... pad V->V Pad the input video.
... perms V->V Set permissions for the output video frame.
T.. perspective V->V Correct the perspective of video.
... phase V->V Phase shift fields.
... pixdesctest V->V Test pixel format definitions.
T.C pp V->V Filter video using libpostproc.
... psnr VV->V Calculate the PSNR between two video streams.
... pullup V->V Pullup from field sequence to frames.
T.. removelogo V->V Remove a TV logo based on a mask image.
TSC rotate V->V Rotate the input image.
T.. sab V->V Apply shape adaptive blur.
... scale V->V Scale the input video size and/or convert the image format.
... select V->N 选择视频帧并传给输出
... sendcmd V->V Send commands to filters.
... separatefields V->V Split input video frames into fields.
... setdar V->V Set the frame display aspect ratio.
... setfield V->V Force field for the output video frame.
... setpts V->V Set PTS for the output video frame.
... setsar V->V Set the pixel sample aspect ratio.
... settb V->V Set timebase for the video output link.
... showinfo V->V Show textual information for each video frame.
... shuffleplanes V->V Shuffle video planes
T.. smartblur V->V Blur the input video without impacting the outlines.
... split V->N Pass on the input to N video outputs.
T.C spp V->V Apply a simple post processing filter.
... stereo3d V->V Convert video stereoscopic 3D view.
... super2xsai V->V Scale the input by 2x using the Super2xSaI pixel art algorithm.
... swapuv V->V Swap U and V components.
... telecine V->V Apply a telecine pattern.
... thumbnail V->V Select the most representative frame in a given sequence of consecutive frames.
... tile V->V Tile several successive frames together.
... tinterlace V->V Perform temporal field interlacing.
.S. transpose V->V Transpose input video.
... trim V->V Pick one continuous section from the input, drop the rest.
T.. unsharp V->V Sharpen or blur the input video.
... vflip V->V Flip the input video vertically.
T.. vignette V->V Make or reverse a vignette effect.
T.. w3fdif V->V Apply Martin Weston three field deinterlace.
TS. yadif V->V 对输入图像去隔行
... cellauto |->V Create pattern generated by an elementary cellular automaton.
..C color |->V Provide an uniformly colored input.
... haldclutsrc |->V Provide an identity Hald CLUT.
... life |->V Create life.
... mandelbrot |->V Render a Mandelbrot fractal.
... mptestsrc |->V Generate various test pattern.
... nullsrc |->V Null video source, return unprocessed video frames.
... rgbtestsrc |->V Generate RGB test pattern.
... smptebars |->V Generate SMPTE color bars.
... smptehdbars |->V Generate SMPTE HD color bars.
... testsrc |->V Generate test pattern.
... nullsink V->| Do absolutely nothing with the input video.
... avectorscope A->V Convert input audio to vectorscope video output.
... concat N->N Concatenate audio and video streams.
... showspectrum A->V Convert input audio to a spectrum video output.
... showwaves A->V Convert input audio to a video output.
... amovie |->N Read audio from a movie source.
... movie |->N Read from a movie source.
... ffbuffersink V->| Buffer video frames, and make them available to the end of the filter graph.
... ffabuffersink A->| Buffer audio frames, and make them available to the end of the filter graph.
... abuffer |->A Buffer audio frames, and make them accessible to the filterchain.
... buffer |->V Buffer video frames, and make them accessible to the filterchain.
... abuffersink A->| Buffer audio frames, and make them available to the end of the filter graph.
... buffersink V->| Buffer video frames, and make them available to the end of the filter graph.
... afifo A->A Buffer input frames and send them when they are requested.
... fifo V->V Buffer input images and send them when they are requested.
4. 其它滤镜示例
Fancy Filtering Examples （http://trac.ffmpeg.org/wiki/FancyFilteringExamples）
– 各种迷幻效果和怪异滤镜的示例
5. 开发自己的滤镜
See FFmpeg filter HOWTO（http://blog.chinaunix.net/uid-26000296-id-3068068.html）
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