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 3, 2009 under Tech Tips |
If you want to gain quick insight into the basic properties of a video file from the Linux command line, there’s a few really easy methods. The information you might be interested in are audio and video codecs, resolution, frame rates, bitrates, etc.
Using mplayer, you can see some basic information about a video file. For example, the following video is using the WMV3 video codec at the resolution of 1280×720 (720p), the bitrate of 3000 kbps, etc.
mplayer video.wmv -vo null -ao null -frames 0 2>&1 /dev/null | egrep "(VIDEO|AUDIO)"
VIDEO: [WMV3] 1280x720 24bpp 1000.000 fps 3000.0 kbps (366.2 kbyte/s)
AUDIO: 44100 Hz, 2 ch, s16le, 96.0 kbit/6.80% (ratio: 12003->176400)
The audio rate is shown to be 44100 Hz using 2-Channel stereo, but the codec is not listed. You can get additional information with the -identify option.
mplayer video.wmv -identify -vo null -ao null -frames 0 2>&1 /dev/null | egrep "(^ID|VIDEO|AUDIO)"
ID_AUDIO_ID=1
ID_VIDEO_ID=2
VIDEO: [WMV3] 1280x720 24bpp 1000.000 fps 3000.0 kbps (366.2 kbyte/s)
ID_CLIP_INFO_NAME0=name
ID_CLIP_INFO_VALUE0=
ID_CLIP_INFO_NAME1=author
ID_CLIP_INFO_VALUE1=
ID_CLIP_INFO_NAME2=copyright
ID_CLIP_INFO_VALUE2=
ID_CLIP_INFO_NAME3=comments
ID_CLIP_INFO_VALUE3=
ID_CLIP_INFO_N=4
ID_FILENAME=video.wmv
ID_DEMUXER=asf
ID_VIDEO_FORMAT=WMV3
ID_VIDEO_BITRATE=3000000
ID_VIDEO_WIDTH=1280
ID_VIDEO_HEIGHT=720
ID_VIDEO_FPS=1000.000
ID_VIDEO_ASPECT=1.7778
ID_AUDIO_FORMAT=353
ID_AUDIO_BITRATE=0
ID_AUDIO_RATE=0
ID_AUDIO_NCH=0
ID_LENGTH=2116.00
ID_VIDEO_ASPECT=1.7778
ID_VIDEO_CODEC=wmv9dmo
AUDIO: 44100 Hz, 2 ch, s16le, 96.0 kbit/6.80% (ratio: 12003->176400)
ID_AUDIO_BITRATE=96024
ID_AUDIO_RATE=44100
ID_AUDIO_NCH=2
ID_AUDIO_CODEC=ffwmav2
Another great tool for identifying video attributes is idvid. idvid comes with the tovid package, so be sure to install it from your repository. It is a bit slow, but the output is very clean and easy to interpret.
idvid video.wmv
--------------------------------
idvid
Video identification script
Part of the tovid suite, version 0.31
http://www.tovid.org
--------------------------------
Analyzing file: 'video.wmv'. This may take several minutes...
=========================================================
File: video.wmv
Width: 1280 pixels
Height: 720 pixels
Aspect ratio: 1.77:1
Frames: 63352
Duration: 00:35:13 hours/mins/secs
Framerate: 1000.000 frames per second
Video format: WMV3
Video bitrate: 3000000 bits per second
---------------------------
Audio track 1 (Stream 0.0, AID 0):
---------------------------
Codec: wmav2
Bitrate: 0000 bits per second
Sampling rate: 44100 Hz
=========================================================
Audio is compliant with the following formats:
Not compliant with (S)VCD or DVD
Video is compliant with the following formats:
Not compliant with (S)VCD or DVD
This video does not seem to be compliant with (S)VCD or DVD
standards. If you burn it to a video disc, it may not work.
=========================================================
Finally, another tool that works very well is exiftool. It’s available in the libimage-exiftool-perl package. The output is also very straight forward, and easy to interpret. It’s also a lot faster than idvid because the tool only displays metadata, which in some cases can be misleading. Mplayer and tovid actually probe the video, providing very accurate information at the cost of speed.
exiftool video.wmv
ExifTool Version Number : 7.30
File Name : video.wmv
Directory : .
File Modification Date/Time : 2009:04:20 09:21:58
File Type : WMV
MIME Type : video/x-ms-wmv
File ID : 12341234-1234-1234-1234-123412341234
File Size : 823200182
Creation Date : 2009:03:31 02:52:55Z
Data Packets : 102833
Play Duration : 35:16
Send Duration : 35:13
Preroll : 3000
Flags : 2
Min Packet Size : 8000
Max Packet Size : 8000
Max Bitrate : 3122812
Is VBR : False
Audio Codec Name : Windows Media Audio 9.2
Audio Codec Description : 96 kbps, 44 kHz, stereo 1-pass CBR
Video Codec Name : Windows Media Video 9
Video Codec Description : Professional
Audio Codec ID : Windows Media Audio V2 V7 V8 V9 / DivX audio (WMA) / Alex AC3 Audio
Audio Channels : 2
Audio Sample Rate : 44100
Stream Type : Video
Error Correction Type : No Error Correction
Time Offset : 0 s
Stream Number : 2
Image Width : 1280
Image Height : 720
Title :
Author :
Copyright :
Description :
Rating :
Image Size : 1280x720
As always, comments and additional tips are welcome!
