Re: Looking at Opus for MP3 replacement and have questions
Reply #17 – 2016-11-14 10:39:26
As for what can be easily misunderstood about frame bitrate: The mp3 bitstream is a stream of frames. The meaning of frames however comes in two flavors. What usually is thought of is the meaning of frames as containers for the data. frames in this sense are restricted to certain frame bitrates like 192, 224, 256, 320 kbps (the maximum). And this is what you are told of when looking at the Lame encoding statistics. The audio data however which belong to a certain frame are not necessarily contained in the corresponding container frame. They can be located (within certain restrictions) also in neighboring containers. This allows for a local audio data bitrate of more than 400 kbps. The statistics however doesn't tell you about this (my lame variant does when using the --frameAnalysis option). With my lame variant I take care that this maximum audio data rate is possible to the outmost extent, But also this shouldn't be overestimated. As shadowking writes you'll probably be fine with lower bitrates than 256 kbps even with mp3. I second this. I participated in the last public mp3 listening test @128kbps and nearly everything was fine to me. I am sensitive to certain tonal problems however that's why I take special care of them. lame3995o is fine with them using -Q2 (~192 kbps). I personally use -Q1 because I'm a bit paranoid (= want to be very much on the safe side) and storage space is no issue for me. /mmt is sensitive to pre-echo issues in an extraordinary way, but as long as you aren't I wouldn't care about his results. Try to ABX castanets music. In case everything is fine to you I'd ignore pre-echo when using a well-established encoder. Same goes for my personal tonal problems. As for Opus vs. mp3 the advantage of Opus is with low and very moderate bitrates. As long as you're using bitrates >=150 kbps on average I wouldn't expect Opus to be superior. At bitrates around 150 kbps a good AAC encoder would be my favorite, at bitrates around 200 kbps or more I 'd use a good mp3 or AAC encoder.