View source for Ffmpeg notes

{{#set: Section=Code Notes|Date=2021}}

=FFMPEG=
==Encoding For Raspberry Pi==
https://raspberrypi.stackexchange.com/questions/3471/omxplayer-h-264-bitrates-and-encoding-settings-for-stutter-free-playback

==mosaic==
Following https://trac.ffmpeg.org/wiki/Create%20a%20mosaic%20out%20of%20several%20input%20videos

For 2 videos, side by side.
<pre>
ffmpeg -i left.mp4 -i right.mp4 -filter_complex " \
nullsrc=size=3840x1080 [base];\
[0:v] setpts=PTS-STARTPTS, scale=1920x1080 [left]; \
[1:v] setpts=PTS-STARTPTS, scale=1920x1080 [right]; \
[base][left] overlay=shortest=1 [tmp1]; \
[tmp1][right] overlay=shortest=1:x=1920" -c:v libx264 mosaic.mp4

</pre>


==screenshots==
key: s  and 
 -vf screenshot 

==FFMPEG encoding examples==

=== Screen cast to .webm ===

Using ''x11grab'' to video grab your display and using ''ALSA'' for sound. First we create lossless raw file {{ic|test.mkv}}.

 $ ffmpeg -f x11grab -r 30 -i :0.0 -f alsa -i hw:0,0 -acodec flac -vcodec ffvhuff test.mkv


Then we process this {{ic|test.mkv}} file into a smaller {{ic|test.webm}} end product. Complex switches like {{ic|c:a}} and {{ic|c:v}} convert the stream into what's needed for [http://en.wikipedia.org/wiki/WebM WebM].

 $ ffmpeg -y -i test.mkv -c:a libvorbis -q:a 3 -c:v libvpx -b:v 2000k test.webm

See https://github.com/kaihendry/recordmydesktop2.0/ for a more fleshed out example.

=== Recording webcam ===

FFmpeg supports grabbing input from Video4Linux2 devices.  The following command will record a video from the webcam, assuming that the webcam is correctly recognized under {{ic|/dev/video0}}:

 $ ffmpeg -f v4l2 -s 640x480 -i /dev/video0 ''output''.mpg

The above produces a silent video. It is also possible to include audio sources from a microphone.  The following command will include a stream from the default [[Advanced Linux Sound Architecture|ALSA]] recording device into the video:

 $ ffmpeg -f alsa -i default -f v4l2 -s 640x480 -i /dev/video0 ''output''.mpg



=== VOB to any container ===

Concatenate the desired [[Wikipedia:VOB|VOB]] files into a single VOB file: 
 $ cat ''video-1''.VOB ''video-2''.VOB ''video-3''.VOB > ''output''.VOB
Concatenate and then pipe the output VOB to FFmpeg to use a different format:
 $ cat ''video-1''.VOB ''video-2''.VOB ''video-3''.VOB > ''output''.VOB | ffmpeg -i ...

=== x264 lossless ===

The ''ultrafast'' preset will provide the fastest encoding and is useful for quick capturing (such as screencasting):
 $ ffmpeg -i input -vcodec libx264 -preset ultrafast -qp 0 -acodec copy ''output.mkv''
On the opposite end of the preset spectrum is ''veryslow'' and will encode slower than ''ultrafast'' but provide a smaller output file size:
 $ ffmpeg -i input -vcodec libx264 -preset veryslow -qp 0 -acodec copy ''output.mkv''
Both examples will provide the same quality output.

=== Single-pass MPEG-2 (near lossless) ===

Allow FFmpeg to automatically set DVD standardized parameters. Encode to DVD [[Wikipedia:MPEG-2|MPEG-2]] at a frame rate of 30 frames/second:

 $ ffmpeg -i ''video''.VOB -target ntsc-dvd -q:a 0 -q:v 0 ''output''.mpg

Encode to DVD MPEG-2 at a frame rate of 24 frames/second:

 $ ffmpeg -i ''video''.VOB -target film-dvd -q:a 0 -q:v 0 ''output''.mpg

=== Volume gain ===

Change the audio volume in multiples of 256 where '''256 = 100%''' (normal) volume. Additional values such as 400 are also valid options. 
 -vol 256  = 100%
 -vol 512  = 200%
 -vol 768  = 300%
 -vol 1024 = 400%
 -vol 2048 = 800%

To double the volume '''(512 = 200%)''' of an [[Wikipedia:Mp3|MP3]] file:
 $ ffmpeg -i ''file''.mp3 -vol 512 ''louder file''.mp3

To quadruple the volume '''(1024 = 400%)''' of an [[Wikipedia:Ogg|Ogg]] file:
 $ ffmpeg -i ''file''.ogg -vol 1024 ''louder file''.ogg

Note that gain metadata is only written to the output file. Unlike mp3gain or ogggain, the source sound file is untouched.




==video codec /ffmpeg resources==
http://ffmpeg.org/

https://www.virag.si/2012/01/web-video-encoding-tutorial-with-ffmpeg-0-9/

=== trnascode audio to aac===
 ffmpeg -i test_4chan_2.wav -acodec libfdk_aac -b:a 384k test_4chan_2.mkv

bit rates: for multichannel: 384k; for setero: 128k

encoders: libfdk_aac (the highest quality), libfaac

commor containers: m4a (mp4 for audio), mkv 

https://trac.ffmpeg.org/wiki/AACEncodingGuide

=== burn subtitles ===
 ffmpeg -i video.avi -vf "ass=subtitle.ass" out.avi

===generate video w/ color===
 ffmpeg -filter_complex 'color=c=red' -t 5 out.mkv

===trim video===
 ffmpeg -i video.avi -vcodec copy -acodec copy -ss 00:00:00 -t 00:00:04 trimmed_video.avi
will start at 00:00:00 and last until 00:00:04

===extract audio only===
-vn - video no
 ffmpeg -i input.ogv -vn audio-out.ogg


===extract video only===
-an - audio no
 ffmpeg -i input.ogv -an video-out.ogv

===no subtitetles===
-sn - subtutiles no
 ffmpeg -i file.mkv -map 0 -sn file.m4v



===join audio and video===
 ffmpeg -i audio.wav -i video.mp4 -acodec copy -vcodec copy output.mp4

===convert to webm===

quick and dirty
 ffmpeg -i input.mp4 -acodec libvorbis -vcode libvpx -f webm output.webm

===convert to ogv===

 ffmpeg -i input.mp4 -acodec libvorbis -vcodec libtheora -f ogv output.ogv


 ffmpeg -i infile.mov -acodec libvorbis -ac 1 -b:a 96k -ar 44100 -vcodec libtheora -b:v 1000k -s 640x360 -g 30 out-file.ogv


<b>¿What is the best video bit rate for web??</b>

===convert to mp4===
 ffmpeg -i out-file.mov -acodec libmp3lame -b:a 96k -ar 44100 -ac 1 -vcodec libx264 -b:v 250k -s 640x360 out-file.mp4


===vpre===

 -vpre = video preset
 -vpre slower -vpre main  ??

The preset files are stored in different places, depending on what OS you have.
If you search your computer for: libx264-slow_firstpass.ffpreset you can hopefully find the folder with them in.

You need to create a separate preset file for the codec you're trying to use.
http://www.ffmpeg.org/ffmpeg-doc.html#SEC13


===using -vpre ipod640 ipod preset===
 ffmpeg -i video_source_file.ext -vcodec libx264 -vpre hq -vpre ipod640 -b:v 250k -bt 50k -acodec libfaac -b:a 56k -ac 2 -s 480x320 video_out_file.mp4


===Examples===
https://wiki.archlinux.org/index.php/FFmpeg
http://www.catswhocode.com/blog/19-ffmpeg-commands-for-all-needs

===enconde for web EXAMPLES===

For mp4 (H.264 / ACC):

ffmpeg -i INPUTFILE -b 1500k -vcodec libx264 -vpre slow -vpre baseline -g 30 "OUTPUTFILE.mp4"
For webm (VP8 / Vorbis):

ffmpeg -i "INPUTFILE"  -b 1500k -vcodec libvpx -acodec libvorbis -ab 160000 -f webm -g 30 "OUTPUTFILE.webm"
For ogv (Theora / Vorbis):

ffmpeg -i "INPUTFILE" -b 1500k -vcodec libtheora -acodec libvorbis -ab 160000 -g 30 "OUTPUTFILE.ogv"

==video w/ 4 audio channels==

    mkv - matroska

    acc audio codec w/ high bit rate encoder

    + generorous cache space

    power saving  - off: smartctl - change smart attributes

    screen saver off
=== test ===
created 4chan wav

ecasound can play it 
 ecasound -f 16,4,44100 -i 4chn.wav -o jack

but mplayer not yet http://www.mplayerhq.hu/DOCS/HTML/en/advaudio-channels.html

===encoders===
* aac - libfaac    
* 


==mplayer==
some tricks and treats

 -osdlevel=0 
disables all the visual elements like progress bars, etc


==Technical aspects(bit rates, sizes,etc)==

===bit rates===
http://www.ezs3.com/public/What_bitrate_should_I_use_when_encoding_my_video_How_do_I_optimize_my_video_for_the_web.cfm

<table cellpadding="5" border="2">
	<tr>
		<td bgcolor="#CCE6FF"><b>Output size</b></td>
		<td bgcolor="#99FF99"><b>Bitrate</b></td>
		<td bgcolor="#FFD6FF"><b>Filesize</b></td>
	</tr>
		<tr><td bgcolor="#CCE6FF">320x240 pixels</td>
		<td bgcolor="#99FF99">400 kbps</td>
		<td bgcolor="#FFD6FF">3MB / minute</td>
	</tr>
	
		<tr><td bgcolor="#CCE6FF">480x270 pixels</td>
		<td bgcolor="#99FF99">700 kbps</td>
		<td bgcolor="#FFD6FF">5MB / minute</td>
	</tr>
	
		<tr><td bgcolor="#CCE6FF">1024 x 576 pixels</td>
		<td bgcolor="#99FF99">1500 kbps</td>
		<td bgcolor="#FFD6FF">11MB / minute</td>
	</tr>
	
		<tr><td bgcolor="#CCE6FF">1280x720 pixels</td>
		<td bgcolor="#99FF99">2500 kbps</td>
		<td bgcolor="#FFD6FF">19MB / minute</td>
	</tr>
	
		<tr><td bgcolor="#CCE6FF">1920x1080 pixels</td>
		<td bgcolor="#99FF99">4000 kbps</td>
		<td bgcolor="#FFD6FF">30MB / minute</td>
	</tr>
</table>

===Standard web video pixel dimensions===

http://phildawson.tumblr.com/post/44238901/standard-web-video-pixel-dimensions


<table width="100%"><tr><th width="50%">16:9</th>
<th width="50%">4:3</th>
</tr><tr><td>1920 x 1080 (1080p)</td>
<td>-</td>
</tr><tr><td><strong>1280 x 720</strong> (720p)</td>
<td>-</td>
</tr><tr><td><strong>960 x 540</strong> (540p)</td>
<td>-</td>
</tr><tr><td><strong>720 x 405</strong></td>
<td>-</td>
</tr><tr><td><strong>640 x 360</strong></td>
<td><strong>640 x 480</strong></td>
</tr><tr><td>560 x 315</td>
<td>560 x 420</td>
</tr><tr><td><strong>480 x 270</strong></td>
<td><strong>480 x 360</strong></td>
</tr><tr><td><strong>400 x 225</strong></td>
<td>400 x 300</td>
</tr><tr><td>320 x 180</td>
<td><strong>320 x 240</strong></td>
</tr><tr><td>240 x 135</td>
<td>240 x 180</td>
</tr><tr><td>160 x 90</td>
<td>160 x 120</td>
</tr><tr><td>-</td>
<td>120 x 90</td>
</tr><tr><td>-</td>
<td>100 x 75</td>
</tr><tr><td>80 x 45</td>
<td>80 x 60</td>
</tr><tr><td>-</td>
<td>60 x 45</td>
</tr></table><br/>