[theora-dev] new user, video fade in issue
Benjamin M. Schwartz
bmschwar at fas.harvard.edu
Thu Oct 14 13:33:16 PDT 2010
There are a few potential issues involved.
1. Your video starts out with digital black. Theora responds by
producing a single frame of black, and then zero-byte "dup frames"
indicating that nothing has changed. Some players are broken and don't
handle these frames correctly. Correctly working players, such as
Firefox, shouldn't have a problem, though.
2. You are using ffmpeg for muxing. (ffmpeg still uses the libtheora
encoder, but does the Ogg encapsulation itself.) The ffmpeg ogg muxer has
had problems in the past, though I don't know its exact status in 0.6. We
generally recommend using ffmpeg2theora instead of ffmpeg, due to a
better-tested ogg muxer and a theora-centric command-line interface.
3. Constant black takes very little bitrate, while the fade might take
much more. The sudden change in bitrate could confuse the buffering
algorithms in network players. You can mitigate this to some degree by
encoding with a target bitrate and buffer constraint.
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