On 26-Jan-2010, at 20:19, Kieran Kunhya wrote: > Older macs without H.264 hardware acceleration also have a very basic version > of the spec through Quicktime because Apple don't seem to fix any bugs with > it.
It’s not just older Macs. Basically, if you don’t restrict yourself to Baseline you’re asking for trouble at the moment. Now, for a lot of web video, Baseline is absolutely fine, though for higher-resolution stuff a different profile would probably be preferable. QuickTime X, shipping with Snow Leopard, and providing the accelerated H.264 abstraction and <video /> support works well in all of my tests. That’s the easy part. iTunes links against QuickTime 7, which is what Leopard and Tiger users (anybody on a PPC Mac, or the rapidly shrinking proportion of people who *won’t* upgrade anyway), and this has noticeable issues with Main content. The Apple TV, which technically runs Tiger, also has problems, to the point that I can reproducibly cause mine to reboot by feeding it iPlayer content retrieved via RTMP and swapped out from its FLV container to ISO media (and I’ve jumped through enough transcoding runs to be pretty sure that it’s Main which trips it up, rather than some container oddities). That said, most PPC Macs will struggle with HD content whatever the profile and decoder, so there’s a limit to the woes in a roundabout way. I haven’t experimented with Win7’s decoder yet, but I suspect that for the time being the answer is to stick with Baseline. [For what it’s worth, all of my encoding tests have been with ffmpeg+x264]. Having said all that, my entirely subjective conclusions at the moment are that the 720p video I get out of ffmpeg+x264 when encoded as Baseline at around 3Mbps[0] compares extremely favourably to the iPlayer HD content (which is High profile, if memory serves) at the same bitrate. I don’t know whether this is down to me not being able to spot the difference from 10 inches away from the screen, whether it’s that x264 is a better encoder than whatever Red Bee uses, or whether it’s simply the case that High Profile is used because Flash can decode it more efficiently[1] than if it were Baseline. Also, noting that at 720p25, 3Mbps ought to be enough! M. [0] Combined audio+video. 160Kbps audio in my tests. Can’t recall what iPlayer HD uses. [1] I’d dread to see Flash decoding that video less efficiently… - Sent via the backstage.bbc.co.uk discussion group. To unsubscribe, please visit http://backstage.bbc.co.uk/archives/2005/01/mailing_list.html. Unofficial list archive: http://www.mail-archive.com/backstage@lists.bbc.co.uk/
