Converting 16:9 content to QCIF ?
Ok, this has been a thorn in my side and I have been doing a bit of research and tests with out much luck so far.
The issue is taking content that is shot in HD and converting it to the mobile phone screen but keeping the proper aspect of the HD content. This leads to a few issues, first of all QCIF (Quarter Common Intermediate format – 176×144) which is at 4:3 aspect ratio.
A test clip im using is at the resolution of 1280×544, its not quite 720p resolution which is 1280×720 but thats besides the point, taking that resolution and fitting it into QCIF causes the aspect of the HD clip to fit to the 4:3 ratio.
The problem is encoding it at a lower res than 176×144 can cause issues with some mobile phones, ie QCIF is a very strict standard resolution that mobile phones have stuck to and some players blow up if its not at the proper res.
What im trying to figure out is how to convert down the clip and use -padtop , -padbottom and -padcolor ffmpeg settings which are supposed to create crop bars for you in black. I have yet to get a result that I like so far. So Im wondering if anyone has a suggestion to do this with either ffmpeg or mencoder.
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It takes 2 or 3 passes to do it right. If you don’t know the dimensions you need to do a pass with ffmpeg or another program to parse the original dimensions (w and h) from the output. Then you need a pass without setting the size but setting padtop and padbottom to p, where 4(h + 2p) = 3w. And I think the default value for padcolor is black, which should be fine. Then you have a video with a 4:3 aspect which you transcode to 3gp in another ffmpeg pass using -s qcif.
By the way, I haven’t had much luck with Darwin streaming on mobile. The presence of a hinted audio track caused weird and ugly effects on the mobiles I tested with. I saw the same problem with streams from the site http://www.zoovision.com. The site eyeka.com seems to deal with this issue by building their own J2ME player and only showing the streaming links to their player. I don’t have a phone which supports their player, though.
One other issue which could block you is the operator. See this cached page for someone’s test results (though note that there’s what I hope is a typo – the rtsp port is 554, not 551): http://tinyurl.com/2z37l9