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FFmpeg Tricks You Should Know About

October 11th, 2010 4 comments

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

Command Line Currency Converter For Linux

March 19th, 2010 2 comments

currency-convertMany times I prefer to just work from the shell. The ~/.bashrc file is a great place to put functions if you are using them regularly.

Let’s build a cool command line currency converter using google’s currency converter. You might require wget or curl and sed to do this.

Just run the following command in terminal.

wget -qO- "http://www.google.com/finance/converter?a=1&from=usd&to=inr&hl=es" |  sed '/res/!d;s/<[^>]*>//g';

This will convert 1 USD to INR (Indian Rupee).
Output:

1 USD = 45.4950 INR

What we are doing is, query google using wget and parse the output using sed.

You can use curl as well:

curl -s "http://www.google.com/finance/converter?a=1&from=usd&to=inr&hl=es" |  sed '/res/!d;s/<[^>]*>//g';

Isn’t that a long command. Lets create a cool bash function for the ease use:
Open you ~/.bashrc file in your favorite text editor and add the following lines and save.

currency_convert() {
  wget -qO- "http://www.google.com/finance/converter?a=$1&from=$2&to=$3&hl=es" |  sed '/res/!d;s/<[^>]*>//g';
}

Now Run:

$ currency_convert 10 usd inr
10 USD = 454.9500 INR

If you want to convert to more than one currencies at once, rewrite our function as bellow.

currency_convert() {
  for i in $3
  do
    wget -qO- "http://www.google.com/finance/converter?a=$1&from=$2&to=$i&hl=es" |  sed '/res/!d;s/<[^>]*>//g';
  done
}

Now run:

$ currency_convert 1 usd "inr gbp eur"
1 USD = 45.4950 INR
1 USD = 0.6603 GBP
1 USD = 0.7382 EUR

Happy currency converting :-)

Categories: LINUX Tags: ,

Keep Track Of Configuration Changes Using etckeeper

March 16th, 2010 3 comments

The official etckeeper website says:

etckeeper is a collection of tools to let /etc be stored in a git, mercurial, darcs, or bzr repository. It hooks into apt (and other package managers including yum and pacman-g2) to automatically commit changes made to /etc during package upgrades. It tracks file metadata that revison control systems do not normally support, but that is important for /etc, such as the permissions of /etc/shadow. It’s quite modular and configurable, while also being simple to use if you understand the basics of working with revision control.

Install etckeeper:

Debian/Ubuntu users can install etckeeper and git using apt.

$ sudo apt-get install etckeeper git-core

Configure etckeeper:

Open /etc/etckeeper/etckeeper.conf in your favorite text editor. The first option that you need to look at is VCS, which is the version control system you want to use. By default it’s set to git, but you can change it to hg or bzr depending on your preference.

If you want to specify some git commit options look ‘GIT_COMMIT_OPTIONS’

Another option that you may want to look is AVOID_COMMIT_BEFORE_INSTALL. By default, etckeeper will automatically commit any pending changes when you install packages. You can disable it by setting AVOID_COMMIT_BEFORE_INSTALL to 1.

Also set AVOID_DAILY_AUTOCOMMITS to 1 for avoiding daily auto commit.

Using etckeeper:

Initialize etckeeper:

$ sudo etckeeper init
Initialized empty Git repository in /etc/.git/
$ sudo etckeeper commit -m "Initial import"

This will create a  git repository for /etc, add all files below /etc (except etckeeper ignore list) to that repository and commit (save) the current contents .

Whenever you make a coherent change to your configuration files, you can commit it by calling etckeeper commit:

$ sudo vi /etc/mysql/my.cnf
$ sudo etckeeper commit -m "mysql conf change"

You can view your commits(saves) using simple git commands:

$ cd /etc/
$ sudo git log

or use a git front-end to see the commits:

$ cd /etc/
$ sudo gitk

etckeeper

Do try it out!

Categories: HOW-TOS, LINUX Tags: , ,