Posted by gmendoza on February 13, 2010 under Tech Tips | 
3gp is the container format used when recording video with many mobile phones, which can be a pain when trying to view them using a number of multimedia players. Fortunately, converting videos from 3gp to XviD AVI is easy with FFmpeg.
Usually, there’s not much to the quality of these types of source video files, so many of the more complex video and audio options aren’t needed. A simple FFmpeg command that retains as much quality as possible would look like the following.
ffmpeg -i video.3gp -acodec libmp3lame -vcodec libxvid -qscale 2 -f avi video.avi
Posted by gmendoza on December 15, 2009 under Tech Tips |
Previously, I described how to Extract Audio from Video Files to WAV using Mplayer. Another method using FFmpeg instead of Mplayer was also pointed out in the post titled Add Stereo Audio Tracks to MKV Files, and I figured it would be useful to outline the quick one-step process in a post all by itself.
Here’s an example of extracting the audio from a video file called video.mkv and saving it to a file called audio.wav. This very well could have been an AVI, MPEG, or any other video format that FFmpeg can decode.
ffmpeg -i video.mkv -acodec pcm_s16le -ac 2 audio.wav
It should also be mentioned that your source video file may have multiple audio channels or streams. For example, you may have both English AC3 and DTS channels, but you may also have other audio streams for other languages, directors comments, etc. If you want more control over which stream you are using, first identify them all with ffmpeg.
ffmpeg -i video.mkv
[snipped for brevity]
Input #0, matroska, from 'video.mkv':
Duration: 01:30:38.78, start: 0.000000, bitrate: N/A
Stream #0.0(eng): Video: h264, yuv420p, 1280x720, PAR 1:1 DAR 16:9, 23.98 tbr, 1k tbn, 47.95 tbc
Stream #0.1(eng): Audio: ac3, 48000 Hz, 5.1, s16
Stream #0.2(eng): Subtitle: 0x0000
Stream #0.3(heb): Audio: mp3, 48000 Hz, stereo, s16
Stream #0.4(heb): Subtitle: 0x0000
Stream #0.5: Attachment: 0x0000
Stream #0.6: Attachment: 0x0000
At least one output file must be specified
From the example above, you see that Stream #0.0 is labeled as being an English video stream with h264 encoding. Stream #0.1 and #0.3 are both audio streams, but #0.1 is English AC3 5.1 and #0.3 is Hebrew MP3 stereo. Simply reference the stream id with the -map option in the following format.
ffmpeg -i video.mkv -map 0:1 -acodec pcm_s16le -ac 2 audio.wav
[snipped for brevity]
Output #0, wav, to 'audio.wav':
Stream #0.0(eng): Audio: pcm_s16le, 48000 Hz, stereo, s16, 1536 kb/s
Stream mapping:
Stream #0.1 -> #0.0
[snipped for brevity]
Now that you have a PCM WAV file, you can manipulated it however you like, e.g. encode to MP3, OGG, FLAC, etc.
lame -V0 -q0 --vbr-new audio.wav audio.mp3
oggenc -q6 audio.wav
flac audio.wav
Posted by gmendoza on November 11, 2009 under Tech Tips |
If you have a video vile that you wish to convert and burn to DVD, you can do so from a Linux command line very easily. We will use FFmpeg for the video conversion, DVDAuthor to create the DVD file system structure, and Growisofs to burn the DVD.
Using FFmpeg, simply specify your input file, the target format, resolution and an output file name. While the following is an over simplified example, it will more than likely work very nicely in most scenarios. The source video file is movie.avi, the target will be formatted for NTSC, and a standard DVD resolution of 720×480 will be used to create a new video file called movie.mpg. There are many additional options that FFMpeg can use to increase quality, so be sure to check out the documentation.
ffmpeg -i movie.avi -target ntsc-video -s 720x480 movie.mpg
Next, you will need to take your new movie.mpg file, and create a DVD file structure that you will burn to disc. Just create a folder that will serve as the parent directory of your DVD. I Like to name it after the title of the movie. Then you will use dvdauthor to create a title set and table of contents and no DVD menus. The movie will just play. :-)
mkdir MOVIE_TITLE
dvdauthor -o MOVIE_TITLE/ -t movie.mpg
dvdauthor -o MOVIE_TITLE/ -T
The dvdauthor -t option creates a title track in the VIDEO_TS directory. If you list the contents after running the first command, you’ll see the corresponding VTS_01_0.BUP, VTS_01_0.IFO, and VTS_01_X.VOB files. The -T option creates a table of contents for all title sets in the file system, which are listed as VIDEO_TS.BUP and VIDEO_TS.IFO.
You are now ready to burn the DVD. In the following command, we will use the -Z option to burn an initial session to the disc, the -dvd-video option to generate a DVD-Video compliant UDF file system, and the -V option to give the disc a Volume ID. This Volume ID is read by your computer to and displays as a nice human readable title typically underneath the icon representing the disc. The -dvd-video and -V options are actually part of the mkisofs (genisoimage) command sets, so they do not show up in the growisofs man pages.
growisofs -Z /dev/dvdrw -dvd-video -V MOVIE_TITLE MOVIE_TITLE/
Notice, you do not need to generate an ISO file to burn the DVD. This would only waste space if your intention is not to distribute or store the video as a disc image. To create the image however, that’s as easy as the following.
genisoimage -o MOVIE_TITLE.iso -dvd-video MOVIE_TITLE/
