Re: [Mlt-devel] encoding for iPhone

[Dan D. <da...@de...>]

On Tue, Mar 2, 2010 at 10:09 AM, Carl Karsten <ca...@pe...> wrote:
> I want to encode PyCon videos as mp4 so that people can use the iTunes
> feed and watch the talks on their iPhone.  Anyone know what res and
> bitrate options I should use?   here is my current line:
>
> melt  -profile dv_ntsc foo.mlt -consumer avformat: foo.mp4

You do not want to keep all the attributes of the dv_ntsc profile. You
want to use 432x320 for 4:3 or 480x320 for 16:9 as maximum resolution
- you can go lower, e.g. 320x240. If your XML project has stuff being
composited, then it will be position-sensitive if not using
percentages or changing aspect ratios. Otherwise, you can safely
append the following consumer properties:
s=432x320 aspect=@4/3
This display aspect property setting forces the sample aspect to be
recomputed and override the profile, which is what you want.
If you have position-sensitive stuff in your xml project, then you
need to run it as:

melt -profile something consumer:path/to/your.mlt profile=dv_ntsc
-consumer avformat:...

> acodec=libmp3lame ab=128k ar=44100 vcodec=mpeg4 minrate=0 b=900k

Usually, AAC is used for audio encoding on iPod/iPhone, and H.264 for
video encoding.
acodec=aac vcodec=libx264

> progressive=1 deinterlace_method=onefield

why onefield and not the superior yadif? remove the property to let it
default to yadif

> I don't have an iphone, so I can't really try stuff and test.

You should also add the following consumer property to configure x264
in a manner compliant with iphone:
vpre=/usr/share/ffmpeg/libx264-ipod640.ffpreset

-- 
+-DRD-+