2002-08-02 11:23:05 +00:00
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OUTDATED
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--------
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2001-01-11 09:42:17 +00:00
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What I propose for EOS condition is th following: As is stands, EOS is a
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flag in a buffer. However, it's also a signal from an element, which is
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odd. What I propose is that EOS become a pad thing. Here's how it would
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work:
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When a source has a final buffer, it marks it as EOS. It passes this on
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through the pad, and the pads set a 'pending' EOS state on the way
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through. When another push or pull happens, only then does the pad signal
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EOS. This means that EOS doesn't happen until the buffer has passed all
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the way to the end, and a request for another buffer is starting to work
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its way back. It gets stopped almost immediately.
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This gets a bit messy in complex cases, haven't thought them all out.
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Assuming everything is reasonably symmetric, it should work out cleanly.
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We may have to add the ability to force buffers to pass even post EOS, but
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that sounds like a hack.
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Example: DVD
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============
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------------ |-------|
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-| mpeg2dec |-----| |
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------------------------ / ------------ | |
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| video0|------/ ------------- | | -------------
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| | -| subtitle0 |-----| merge |-------| videosink |
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| subtitle0|------/ ------------- | | -------------
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---------- | | ------------- | |
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| dvdsrc |---| mpeg2parse subtitle1|--------| subtitle1 |-----| |
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---------- | | ------------- |-------|
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| audio0|--------\ ----------- |----------|
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| | -| ac3dec0 |-----| |
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| audio1|-------\ ----------- | | -------------
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------------------------ \ ----------- | switcher |----| audiosink |
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-| ac3dec1 |-----| | -------------
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----------- |----------|
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When dvdsrc reads its last buffer, it sets EOS on the buffer and passes it. The pad (probably audio1,
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since video and audio are interleaved and subtitles don't usually end up at the end of a movie) would
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set EOS pending, and pass it to mpeg2dec which would pass the EOS to the merge. Merge would then ask
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for a buffer from subtitle1, since that's the one we're showing subtitles on right now. It would then
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pull from the mpeg2parse. This would cause a switch back the parser, who's next task is to go and set
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all the output pads to EOS. It may have to accomplish this by sending a zero-byte buffer.
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Well, this example isn't actually very good. I'll go ahead and implement it, and we can see what
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happens. The current setup is so lacking that anything is better....
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