Formatting Video for iPad

This, I have to say, has been one of the most gratifying things to work out in my entire experience of working stuff out. The iPad is an excellent device for consuming media, especially video. The problem is getting video in a format suitable for the iPad without forking over dosh to Apple.

The best I have been able to come up with to date is Handbrake, which has built in modes for the iPad. What it doesn't do is batch convert a whole directory to iPad format.

So joy of joys, I present the Ubuntu commands necessary for this (assuming you have installed the requisite packages all of which are listed in my how to build a custom Live CD posts).

target_resolution="1024x576" &&
target_bitrate="2.5M" &&
minimum_bitrate="0k" &&
maximum_bitrate="3.5M" &&
audio_bitrate="256k" &&
audio_sample_rate="48000" &&
audio_channels="2" &&
input_extension="mkv" &&
number_of_threads="8" &&
for file in *.$input_extension; do \
ffmpeg -y -i "$file" \
-pass 1 -f mp4 \
-s $target_resolution -vcodec libx264 -threads $number_of_threads -b $target_bitrate \
-bt 100k -maxrate $maximum_bitrate -minrate $minimum_bitrate -bufsize 2M \
-flags2 +mixed_refs -flags +loop -cmp +chroma -partitions +parti4x4+partp8x8+partb8x8 -subq 5 -trellis 2 -refs 2 -coder 0 -me_method umh -me_range 90 -keyint_min 25 -sc_threshold 40 -i_qfactor 0.71 \
-rc_eq 'blurCplx^(1-qComp)' -qcomp 0.6 -qmin 10 -qmax 51 -qdiff 4 -level 30 -g 90 -an /dev/null && \
ffmpeg -y  -i "$file" \
-pass 2 -f mp4 \
-acodec libfaac -ar $audio_sample_rate -ab $audio_bitrate -ac $audio_channels \
-s $target_resolution -vcodec libx264 -threads 8  -async 2205 -b $target_bitrate \
-bt 100k -maxrate $maximum_bitrate -minrate $minimum_bitrate -bufsize 2M \
-flags2 +mixed_refs -flags +loop -cmp +chroma -partitions +parti4x4+partp8x8+partb8x8 -subq 5 -trellis 2 -refs 2 -coder 0 -me_method umh -me_range 90 -keyint_min 25 -sc_threshold 40 -i_qfactor 0.71 \
-rc_eq 'blurCplx^(1-qComp)' -qcomp 0.6 -qmin 10 -qmax 51 -qdiff 4 -level 30 -g 90 \
"${file%.$input_extension}.mp4" \
 ; done

You fill in the details between the quotes at the beginning, copy and paste the code into a command line in a directory containing video files of type .input_extension and it will convert all the files to .mp4 suitable for playing on an iPad. All files will have exactly the same resolution and bitrate, which may not be desirable, so check in advance by examining your files.

You can change the target bitrate to whatever you like, within reason, and the iPad will still play the files. You will want to carefully check the aspect ratio of the files going in to make sure that these settings work. If they start in 16:9 this will spit them out in 16:9 at 1024x576. 4:3 files will need the target_resolution changed to "1024x768" for instance.

Don't make the mistake I made of running several instances of this command at the same time - because they will overwrite each others variables.

As a bonus, here are the commands necessary to extract audio from a clip in an iPod/iPhone friendly format:

audio_bitrate="128k" &&
audio_sample_rate="48000" &&
audio_channels="2" &&
input_extension="flv" &&
for file in *.$input_extension; do \
ffmpeg -y -i "$file" -vn \
-acodec libfaac -ar $audio_sample_rate -ab $audio_bitrate -ac $audio_channels \
"${file%.$input_extension}.m4a" \
; done

Same rules apply.