Documentation Inconsistencies about Frame Size about opus

[rillian]

I think some of the confusion here is that the two documents are targetting different applications: real-time communication where latency may be important vs. file encoding for later playback, where quality-for-bitrate is more important than latency or network packet framing overhead.

I'll see if I can clear up the wording. Basically, you should use the default 20 ms frame size for file encoding, and at high bitrates (like 96 kbps stereo).

[jmvalin]

Updated the first wiki page. Don't use larger than 20 ms unless you actually care about fitting more audio per packet. For files, it results in worse quality (as the FAQ states).

[tejasvi8874]

      Updated the first wiki page. Don't use larger than 20 ms unless you actually care about fitting more audio per packet. For files, it results in worse quality (as the FAQ states).

Is quality inversely proportional to frame size? (for later playback purposes)

[rillian]

The relation of quality to frame size is a function with central peak. Larger (and smaller!) frame sizes reduce quality for a given codec bitrate. We recommend 20 ms frame sizes unless you have another technical constraint which is more important than quality.

The frame size is flexible to accommodate special applications, but for normal use 20 ms is the best choice. Frame sizes larger than 20 ms limit the encoder's ability to switch modes in response to signal changes. Frame sizes shorter than 20 ms limit the encoder's ability to exploit redundancy in the less-varying signals. Either way you need more bits to make up the difference.