Monday, 26 March 2012

One liners for encoders

Multimedia capabilities of portable and non PC like devices is growing every day, but mostly limited to variations of MPEG standards variations. On the other hand on PCs there seems to appear a new format once a week.
Luckily there are a few good and free software for converting media formats.

My favourite A/V container is Matroska (.mkv) - can hold multiple .. everything (audio, video, subtitles tracks) :D.
Mkvtoolnix is a awesome toolkit for playing with A/V files - for example splitting & joining files, even from different formats.
GUI is easy to use, so here's some examples of shell tools usage
mkvextract  tracks       example.mkv  1:video.mkv  2:audio.aac 3:english.ass
mkvextract  attachments  example.mkv  1:cover.jpg  2:arial.ttf



For some reason I can't get my TV to play audio from DTS sources.
I used to use FLAC (lossless audio) encoder as a pass-thru for encoding audio to AAC. Here are batches for that - just put them somewhere %PATH% points :

1. Whatever (ffmpeg can read/decode) to FLAC
"C:\Program Files\mkvtoolnix\ffmpeg.exe" -i %1 -vn -sn -acodec flac %2

2. FLAC to HEv1 AAC
@ECHO OFF
cls
set tmp=%CD%
set temp=%CD%
"C:\Program Files\mkvtoolnix\flac.exe" -d -c %1 | "C:\Program Files\mkvtoolnix\neroAacEnc.exe" -he -q 1 -if - -of %2
@PAUSE

The set tmp=%CD% part is useful if you use ramdisk, without it NeroAacEnc uses default "c:\SomeWhere\Temp",
In both batches first parameter is input file, second points to where to write.

I've found a better way for doing that : direct decode whatever audio format to aac
"C:\Program Files\mkvtoolnix\ffmpeg.exe" -i %1 -vn -sn -acodec pcm_s16le -ar 48000 -f wav - | "C:\Program Files\mkvtoolnix\neroAacEnc.exe" -he -q 1 -if - -ignorelength -of %2

And there's also ffmpeg's built in AAC encoder
ffmpeg -i /media/funny.mp4 -vcodec copy -ab 512k -ac 6 -acodec aac -strict experimental /media/funny.mkv


There's a popular opinion around the Net that Nero AAC Encoder gives better results than free libfaac.
Just google for : nero ftp NeroAACCodec-1.5.1.zip - it has encoder version 1.5.4.0 from February 2010.

Help info (-help) says that HEv1/v2 is selected automatically, but I always got LC profile on my encodes, so I started forcing HEv1 (-he) - didn't notice quality difference, but size reduction is significant.

Here's a wine variant (or you can use Linux binaries and skip the "wine") :
wine flac.exe -d -c /media/example.flac | wine neroAacEnc.exe -he -q 1 -if - -of /media/example.aac


Other fun example : got lots of photos from a trip, take a lot of space, so what's the best way to compress them and save on storage space ?
2 pass slow encode from jpg to 1 FPS x264 - got 200MB movie from 900MB of photos, perfect for small SD phone card.
ffmpeg -f image2 -r 1 -i "%d.jpg" -vcodec libx264 -pass 1 -passlogfile /media/1pass -sameq -preset slow /media/temp.mkv

ffmpeg -f image2 -r 1 -i "%d.jpg" -vcodec libx264 -pass 2 -passlogfile /media/1pass -sameq -preset slow -vb 3400k /media/trip.mkv
MPEG (x264 is MPEG4) compression doesn't stores separate frames individually like MJPEG, but looks for similar blocks in neighboring frames and stores differences, plus other complicated size reduction methods of course.
Images have to be named like 1.jpg, 2.jpg .. 10.jpg, .. 999.jpg etc. While first pass is fairly fast, the second encoding can drop to 1-2 FPS with hi-res pics - but size/quality is awesome - or you can use -preset normal.
For bit rate (-vb) I use average file size from the pics list.


Observation : my Philips TV from 5000 series can only display JPEGs compressed without Progressive methode, also can only play mkv with one audio track.

Izismile has option to download their videos in MP4 or FLV format - if you need sources to experiment.

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