Originally Posted by paulkoan

It may not be all that useful for you then. The majority of the script just deals with the file names and looping. The main thrust of the script is in the ffmpeg line:

Code:

ffmpeg -i "$infile" -r pal -s 800x448 -vcodec mpeg4 -qmin 3 -qmax 5 -crf 22 -acodec libfaac -ab 128k -ac 2 -f mp4 "$mp4file"

-i is the input file
-r is the frame rate (using PAL default framerate)
-s is the size. For 16:9 content, this seems to be the best option from the wiki, as it keeps all the horizontal information and puts small borders at the top and bottom (16/9 = 800/448 approx)
-vcodec is the video codec to use - I use mpeg4
-qmin = minimum quantiser
-qmax = max quantiser
-crf = constant rate factor

These three settings influence the quality and bitrate in ways I do not fully get. crf may not even be applicable to mpeg4

-acodec is the audio codec, I am using the libfaac codec for ac3 audio

-ab audio bitrate
-ac audio channels (2=stereo)

-f container format - here I use mp4

"$mp4file" - the last parameter to ffmpeg is the output file.

Video transcoding is a complex topic and I don't even approximate an expert.