Hello, will my quality be the same, if I convert my Blu-ray to mp4 then to ogg as if I just converted directly to ogg from Blu-ray?
Since MP4 is a compressed format, you’re stuck with additional sound damage.
One pass through compression damage is pretty simple, but the real magic is in multi-pass. BluRay already has compressed sound, so if you really offended the sound gods, converting that to MP4 may double the damage.
Sound Compression is only partly about making the data smaller. Its other job is to cleverly hide the damage. That’s why you can listen to relatively heavily compressed MP3 and not know there’s anything wrong until you compare it to the original. Then, suddenly, it doesn’t sound so good. Multi-pass compression can mess up hiding.
That’s what kills people trying to make original content shows with download music. Very few people get away with that.
“How can I make the music on my Podcast sound better? It sounds honky like a cellphone.”
Use better music. iTunes Store has music at extra cost which survives multi-pass compression better and doesn’t have copy restrictions.
Koz
MP4 is lossy compression and OGG is lossy compression. (MP3 is lossy too.) You should avoid multiple generations of lossy compression if possible, and if it’s not possible, at least minimize the number times a file is lossy-compressed. And, if file size is not a concern for you, choose a high bitrate for less compression.
BluRay already has compressed sound
Actually, Blu-Ray supports several [u]lossy and non-lossy formats[/u] so it depends on what formats are on the disc and the tools/decoders you have to extract those files.