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FFmpeg Tricks You Should Know About

October 11th, 2010

ffmpeg

FFmpeg is a complete, cross-platform solution to record, convert and stream audio and video. It includes libavcodec – the leading audio/video codec library. FFmpeg is free software and is licensed under the LGPL or GPL depending on your choice of configuration options.

FFmpeg supports most of the popular formats, we don’t need to worry a lot about that. Formats supported by FFmpeg include MPEG, MPEG-4 (Divx), ASF, AVI, Real Audio/Video and Quicktime. To see a list of all the codecs/formats supported by FFmpeg, run the following command:

ffmpeg -formats

1. X11 grabbing

FFmpeg can grab the X11 display.

ffmpeg -f x11grab -r 24 -s cif -i :0.0 /tmp/out.mpg

0.0 is display.screen number of your X11 server, same as the DISPLAY environment variable.

ffmpeg -f x11grab -r 24 -s cif -i :0.0+10,20 /tmp/out.mpg

0.0 is display.screen number of your X11 server, same as the DISPLAY environment variable. 10 is the x-offset and 20 the y-offset for the grabbing.

ffmpeg -f x11grab -r 25 -s 800x600 -i :0.0 /tmp/outputFile.mpg

2. Convert Pictures To Movie

First, rename your pictures to follow a numerical sequence. For example, img1.jpg, img2.jpg, img3.jpg,… Then you may run:

ffmpeg -f image2 -i img%d.jpg /tmp/a.mpg

Notice that `%d’ is replaced by the image number.

`img%03d.jpg' means the sequence `img001.jpg', `img002.jpg', etc…

If you have large number of pictures to rename, you can use the following command to ease the burden. The command, using the bourne shell syntax, symbolically links all files in the current directory that match *jpg to the `/tmp' directory in the sequence of `img001.jpg', `img002.jpg' and so on.

 x=1; for i in *jpg; do counter=$(printf %03d $x); ln "$i" /tmp/img"$counter".jpg; x=$(($x+1)); done

If you want to sequence them by oldest modified first, substitute $(ls -r -t *jpg) in place of *jpg.

Then run:

  ffmpeg -f image2 -i /tmp/img%03d.jpg /tmp/a.mpg

The same logic is used for any image format that ffmpeg reads.

3. Video Conversions

Quick and dirty convert to flv

ffmpeg -i inputfile.mp4 outputfile.flv

This converts any media ffmpeg handles to flash. It would actually convert anything to anything, it’s based on the file extension. It doesn’t do ANY quality control, sizing, etc, it just does what it thinks is best.

Convert .flv to .3gp

ffmpeg -i file.flv -r 15 -b 128k -s qcif -acodec amr_nb -ar 8000 -ac 1 -ab 13 -f 3gp -y out.3gp

Download YouTube videos as .flv and convert them to .3gp for your mobile phone.

Convert AVI to iPhone MP4

ffmpeg -i [source].avi -f mp4 -vcodec mpeg4 -b 250000 -s 480?320 -acodec aac -ar 24000 -ab 64 -ac 2 [destination].mp4

for 4:3 aspect:

ffmpeg -i source-xvid.avi -s 480x320 -aspect 4:3 -b 768k -ab 64k -ar 22050 -r 30000/1001 OUT.mp4

for 16:9:

ffmpeg -i source-xvid.avi -s 480x320 -aspect 16:9 -b 768k -ab 64k -ar 22050 -r 30000/1001 OUT.mp4

Create a video that is supported by youtube:

ffmpeg -i mymovie.mpg -ar 22050 -acodec libmp3lame -ab 32K -r 25 -s 320x240 -vcodec flv
mytarget.flv

Takes an mpeg video and coverts it to a youtube compatible flv file.
The -r 25 sets the frame rate for PAL, for NTSC use 29.97

4. Audio Conversion

Convert RM file to mp3

ffmpeg -i input.rm -acodec libmp3lame -ab 96k output.mp3

Adjust the bitrate (-ab) as necessary. If omitted FFmpeg will use a default of 64 kb/s.

Converting WMV to MP3 using FFMPEG

ffmpeg -i audio1.wmv audio1.mp3

This will convert audio1.wmv file to audio1.mp3
Converting WMV to FLV using FFMPEG

ffmpeg -i audio1.wmv audio1.flv

This will convert audio1.wmv file to audio1.flv, this will generate only audio content
Converting AMR to MP3 using FFMPEG

ffmpeg -i audio1.amr -ar 22050 audio1.mp3

This will convert audio1.amr file to audio1.mp3 having audio rate 22.05 Khz
Converting aac to mp3 using FFMPEG

ffmpeg -i audio1.aac -ar 22050 -ab 32 audio1.mp3

This will convert audio1.aac to audio1.mp3 having audio rate 22.05 Khz and Audio BitRate 32Khz
Converting aac to mp3 using FFMPEG with MetaData

ffmpeg -i audio1.aac -ar 22050 -ab 32 -map_meta_data audio1.mp3:audio1.aac audio1.mp3

This will convert audio1.aac to audio1.mp3 having audio rate 22.05 Khz and Audio BitRate 32Khz and will copy the meta data from .aac file to .mp3 file

5. Audio Extraction

ffmpeg -i video.avi -f mp3 audio.mp3

Dumping Audio stream from flv (using ffmpeg)

ffmpeg -i input.flv -f mp3 -vn -acodec copy ouput.mp3

6. Record Audio and Video from webcam

To record video run ffmpeg with arguments such as these:

ffmpeg -f video4linux2 -s 320x240 -i /dev/video0 out.mpg

To record both audio and video run ffmpeg with arguments such as these:

ffmpeg -f oss -i /dev/dsp -f video4linux2 -s 320x240 -i /dev/video0 out.mpg

7. Copy Only A Part Of Video

Cut out a piece of film from a file. Choose an arbitrary length and starting time.

ffmpeg -vcodec copy -acodec copy -i orginalfile -ss 00:01:30 -t 0:0:20 newfile

-vcodec, you choose what video codec the new file should be encoded with. Run ffmpeg -formats E to list all available video and audio encoders and file formats.

copy, you choose the video encoder that just copies the file.

-acodec, you choose what audio codec the new file should be encoded with.

copy, you choose the audio encoder that just copies the file.

-i originalfile, you provide the filename of the original file to ffmpeg

-ss 00:01:30, you choose the starting time on the original file in this case 1 min and 30 seconds into the film

-t 0:0:20, you choose the length of the new film

newfile, you choose the name of the file created.

8. Join Multiple Video Files

A few multimedia containers (MPEG-1, MPEG-2 PS, DV) allow to join video files by merely concatenating them.

Hence you may concatenate your multimedia files by first transcoding them to these privileged formats, then using the humble cat command (or the equally humble copy under Windows), and finally transcoding back to your format of choice.

mkfifo orig1.mpg
mkfifo orig2.mpg
ffmpeg -i input1.avi -sameq -y orig1.mpg
ffmpeg -i input2.avi -sameq -y orig2.mpg

Merge files

cat orig1.mpg orig2.mpg | ffmpeg -f mpeg -i - -vcodec copy -acodec copy merged.mpg

Merge and convert to avi

cat orig1.mpg orig2.mpg | ffmpeg -f mpeg -i - -sameq -vcodec mpeg4 -acodec libmp3lame merged.avi

Notice that you should either use -sameq or set a reasonably high bitrate for your intermediate and output files, if you want to preserve video quality.

Also notice that you may avoid the huge intermediate files by taking advantage of named pipes, should your platform support it:

9. Removing Synchronization Problems Between Audio and Video

ffmpeg -i source_audio.mp3 -itsoffset 00:00:10.2 -i source_video.m2v target_video.flv

This assumes that there is a 10.2 sec delay between the video and the audio (delayed).

To extract the original video into a audio and video composites look at the command on extracting audio and video from a movie

Here is more information of how to use ffmpeg:
http://www.ffmpeg.org/ffmpeg-doc.html

  1. October 12th, 2010 at 21:40 | #1

    Number 1 doesn’t seem to work for me:

    $ ffmpeg -f x11grab -s cif -i :0.0 /tmp/out.mpg
    FFmpeg version 0.6, Copyright (c) 2000-2010 the FFmpeg developers
    built on Jul 21 2010 11:19:42 with gcc 4.4.3
    configuration: –prefix=/usr –enable-shared –libdir=/usr/lib64 –shlibdir=/usr/lib64 –incdir=/usr/include –disable-stripping –enable-postproc –enable-gpl –enable-pthreads –enable-libtheora –enable-libvorbis –disable-encoder=vorbis –enable-libvpx –enable-x11grab –enable-runtime-cpudetect –enable-libdc1394 –enable-libschroedinger –enable-librtmp –enable-libmp3lame –enable-libfaad –enable-libopencore-amrnb –enable-libopencore-amrwb –enable-version3 –enable-libx264
    libavutil 50.15. 1 / 50.15. 1
    libavcodec 52.72. 2 / 52.72. 2
    libavformat 52.64. 2 / 52.64. 2
    libavdevice 52. 2. 0 / 52. 2. 0
    libswscale 0.11. 0 / 0.11. 0
    libpostproc 51. 2. 0 / 51. 2. 0
    [x11grab @ 0x1388460]device: :0.0 -> display: :0.0 x: 0 y: 0 width: 352 height: 288
    [x11grab @ 0x1388460]AVParameters don’t have video size and/or rate. Use -s and -r.
    :0.0: Input/output error

    • October 13th, 2010 at 11:29 | #2

      -s and -r parameters have to be specified *before* the -i INPUT
      option, otherwise they are associated to the *next* INPUT/OUTPUT file.

      Try this.

      ffmpeg -f x11grab -r 24 -s svga -i :0.0 /tmp/out.mpg

      refer: http://bit.ly/d9AsXI

  2. darethehair
    October 13th, 2010 at 19:02 | #3

    I like your ‘renaming’ script! It was simpler than the one I had found. However, maybe this would be a bit better?

    x=1; for i in *jpg; do counter=$(printf %03d $x); ln -s “$PWD/$i” /tmp/img”$counter”.jpg; x=$(($x+1)); done

    Changes are:

    1) Symbolic link rather than hard link
    2) Includes fully-qualified path of source image in the symbolic link

    For ‘Canon’ images, the suffix is ‘JPG’ rather than ‘jpg’, but that depends on the camera…

  3. Jahde
    November 4th, 2010 at 07:06 | #4

    Great Post!

  1. October 13th, 2010 at 05:12 | #1
  2. October 14th, 2010 at 02:02 | #2
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