[FFmpeg-trac] #9939(undetermined:new): JPEG 2000 images are decoded twice and needlessly slow

[FFmpeg]

#9939: JPEG 2000 images are decoded twice and needlessly slow
-------------------------------------+-------------------------------------
             Reporter:  Tomas        |                     Type:
  Härdin                             |  enhancement
               Status:  new          |                 Priority:  normal
            Component:               |                  Version:
  undetermined                       |  unspecified
             Keywords:               |               Blocked By:
  j2k,ffmpeg,probe                   |
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
 If ffmpeg is told to decode a single JPEG 2000 image then it will decode
 it twice. If -lowres 2 is specified then it will first decode it at full
 resolution and then at the requested quarter resolution. For lossless JPEG
 2000 this is especially slow.

 {{{
 $ time ./ffmpeg -loglevel error -lowres 2 -i
 smoke_sauna_JPEG2000_SDR_3840x2160p50_YUV444_12bit_Lossless.mov -vframes 1
 -f framecrc -
 #software: Lavf59.32.101
 #tb 0: 1/50
 #media_type 0: video
 #codec_id 0: rawvideo
 #dimensions 0: 960x540
 #sar 0: 1/1
 0,          0,          0,        1,  3110400, 0x5091f9f3

 real    0m7,797s
 user    0m9,841s
 sys     0m0,441s
 }}}

 Dummying out the call to jpeg2000_decode_tile() for the first call to
 jpeg2000_decode_frame() still gives the same results, but much faster:

 {{{
 #software: Lavf59.32.101
 #tb 0: 1/50
 #media_type 0: video
 #codec_id 0: rawvideo
 #dimensions 0: 960x540
 #sar 0: 1/1
 0,          0,          0,        1,  3110400, 0x5091f9f3

 real    0m1,300s
 user    0m3,539s
 sys     0m0,415s
 }}}


 All that the first decode really does is set avctx->pix_fmt. What I'd like
 to see:

 * that jpeg2000_decode_frame() is only called once
 * that jpeg2000_decode_frame() is called with the correct value for lowres
 * that jpeg2000_decode_frame() is allowed to use threads during probing

 The first could be accomplished by caching the decoded frame, or with a
 flag of some kind.

 Commit: 686096739b129c7e3ea26be29c875e0887e58c49 since current master is
 broken in libavutil/x86/tx_float.asm
 Sample:
 ftp://svtopencontent.svt.se/pub/svt_videotestsuite_natural_complexity/REC709/smoke_sauna_JPEG2000_SDR_3840x2160p50_YUV444_12bit_Lossless.mov
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/9939>
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