[mythtv-commits] Ticket #13233: Android Hardware accelerated decode

[MythTV]

#13233: Android Hardware accelerated decode
-----------------------------+-------------------------------
 Reporter:  Peter Bennett    |          Owner:  Peter Bennett
     Type:  Developer Task   |         Status:  assigned
 Priority:  minor            |      Milestone:  unknown
Component:  Ports - Android  |        Version:  Master Head
 Severity:  medium           |     Resolution:
 Keywords:                   |  Ticket locked:  0
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Comment (by Peter Bennett <pbennett@…>):

 In [changeset:"8e34e6e558859b9b5efc3ab43cd6e9716496bcad/mythtv"
 8e34e6e55/mythtv]:
 {{{
 #!CommitTicketReference repository="mythtv"
 revision="8e34e6e558859b9b5efc3ab43cd6e9716496bcad"
 Playback: Prerequisites to support for mediacodec

 Mediacodec is used for hardware decoding on android. It works differently
 from other decoding methods and needs several changes to support the
 different flow.
 1. On NVidia Shield, mediacodec provides built in deinterlace with frame
 doubling.
   This causes a discrepancy between reported framerate and actual
 framerate.
   Changes are made to support detecting and using the double framerate.
 2. Up to now there was always a maximum of one frame released after a
 packet
   was provided to the decoder. Mediacodec releases many frames at a time,
 typically
   15 frames at once after 15 or more packets were sent. Many changes are
 needed to support this.
 3. In conjunction with the previous change, FFmpeg recommend that the code
 always
   read all frames available before sending the next packet. Previously it
 would
   read one frame before sending the next packet. Change to support this.
 5. The existing code uses arcane methods to calculate frame timing from
 the
   packet sent. This causes havoc with mediacodec because of the multiple
 frames
   per packet and the frame doubling. FFmpeg alreay does this work for you,
 correctly.
   Change to use ffmpeg frame timing for ffmeg and mediacodec. Other
 decoding methods
   probably should change as well, but that is not done here.
 7. When skipping forward or back with doubled framerate from mediacodec,
 one frame
   is presented that is a combination of old and new frame. Change to drop
 the first
   4 frames after skipping with doubled framerate to avoid this.
 8. With mediacodec there is sometimes a situation where the decoder will
 neither
   accept a packet nor provide a frame. According to FFmpeg documentation
 this will
   never occur, but it does occur. A short wait and retry in this case
 solves the problem.

 Refs #13233
 }}}

-- 
Ticket URL: <https://code.mythtv.org/trac/ticket/13233#comment:26>
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