ISO too big for (video) dvd

ordealbyfire83 · 03-13-2009, 05:06 PM

Hello,
I have some avi files that I want to put on DVD for playing in a DVD player. I have done the following:

(1) convert the avi file to mpg using ffmpeg--which has the -target [...] function that (supposedly) makes files for e.g. dvd

Code:

ffmpeg -i input.avi -target pal-dvd -aspect 16:9 output.mpg

Problem is, this video is only about an hour and a half long yet the resulting file is 4703713280 bytes (the original avi is something like 700 mb or so).

Code:

dvdauthor --title -o dvd -f output.mpg

Code:

dvdauthor -o dvd -T

Code:

mkisofs -dvd-video -o dvd.iso ./dvd

Now the iso is 4704741376 bytes. K3B complains this file is too big for a dvd. What am I doing wrong? Is this a problem in ffmpeg? Thanks

David the H. · 03-13-2009, 06:05 PM

A DVD-R disk can hold only approximately 4,700,000,000 bytes (apparently there's a small difference between DVD-R and DVD+R though). Your file is just a bit too big for that, especially after adding the DVD menu structure.

What you should probably do is set a slightly lower bitrate in ffmpeg so that the final file size is within DVD capacity. I don't know what the default setting is, so watch the output as ffmpeg runs and you should see what bitrate it's using. Then you can adjust the number downwards with the -b flag.

You could also save some space by reducing the audio bitrate or using a different format. Again, I don't know what the default settings for ffmpeg's dvd presets are, but if it's ac3, for example, you could change it to mp2 and save some more space. Check the dvd video specs for the legal setting ranges. You probably wouldn't get that much savings, but you're only marginally over the line anyway, so it might be enough.

edit: I just ran a test, and the pal-dvd settings are:

video bitrate 6000k
audio format ac3
audio bitrate 480k

So you could save a pretty good amount of space just by setting the audio to mp2 at something like 192k. Unless you're a real audiophile you probably wouldn't notice any difference in sound quality at all. Especially since the source audio is probably already a low-quality mp3 track or somesuch. There's also a large amount of headroom in the video bitrate considering the source. You could use 4000-5000k or even less and probably not affect the quality noticably.