RE: M4A files (from YAMB) = slightly smaller filesize than originalAACs?
I've noticed this with MP4Box as well. I think it filters out ADTS frame headers when adding the AAC audio as a track to the MP4 file, which would account for most of the difference. I would guess YAMB does likewise. It seems to be non-destructive though; when re-exporting the raw streams out of the MP4 file the resulting filesize is identical to the original file. I *haven't* checksummed them though (just thought about doing it) - will run QuickSFV when I get home and report the results, I'm about to leave the office. ___ get_iplayer mailing list get_iplayer@lists.infradead.org http://lists.infradead.org/mailman/listinfo/get_iplayer
Re: M4A files (from YAMB) = slightly smaller filesize than originalAACs?
On 17/05/2011 19:01, Christopher Woods (CustomMade) wrote: I've noticed this with MP4Box as well. I think it filters out ADTS frame headers when adding the AAC audio as a track to the MP4 file, which would account for most of the difference. I would guess YAMB does likewise. It seems to be non-destructive though; when re-exporting the raw streams out of the MP4 file the resulting filesize is identical to the original file. I *haven't* checksummed them though (just thought about doing it) - will run QuickSFV when I get home and report the results, I'm about to leave the office. Yep - I should pointed that out. The ADTS frame headers are there for use in streaming, but when they get stripped you still have the raw AAC audio intact inside the MP4 file - it doesn't get changed in any way, at least not by MP4Box. When I first noticed this, I checksummed ADTS AAC audio going in and out of MP4Box, and it's OK. ___ get_iplayer mailing list get_iplayer@lists.infradead.org http://lists.infradead.org/mailman/listinfo/get_iplayer
RE: M4A files (from YAMB) = slightly smaller filesize than originalAACs?
I'm not going to swear to it, but as long as the conversion is only taking a few seconds, then there's probably nothing to worry about. Hopefully some others will chime in, but conversion to MP3 would take a lot longer (probably several minutes on a current PC? Try it to find out). If you're not transcoding, then you're (hopefully!) not performing a lossy operation on the audio stream. Indeed. Preaching to the choir there, I work with audio on a daily basis juggling probably half a dozen formats, lossy and lossless. I spend seemingly half of my waking hours explaining to people why transcoding their iTunes to MP3 is not a good idea. ___ get_iplayer mailing list get_iplayer@lists.infradead.org http://lists.infradead.org/mailman/listinfo/get_iplayer
