[FFmpeg-trac] #7018(avcodec:new): cc_dec decoder very slow at extracting CEA-708 closed captions from mpeg2ts file

[FFmpeg]

#7018: cc_dec decoder very slow at extracting CEA-708 closed captions from mpeg2ts
file
-------------------------------------+-------------------------------------
             Reporter:  devesh       |                     Type:  defect
               Status:  new          |                 Priority:  normal
            Component:  avcodec      |                  Version:  git-
             Keywords:  cc_dec       |  master
  CEA-708 captions performance       |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
 Summary of the bug: When transcoding an mpeg2ts hdhomerun recording, if I
 ask ffmpeg to also decode the embedded closed captions, processing slows
 down much more than expected.
 How to reproduce:
 {{{
 % time ~/projects/ffmpeg/ffmpeg -f lavfi -i
 "movie=1441_20180209070000.ts[out0+subcc]" out2.srt
 ffmpeg version N-89982-g81d6501be7 Copyright (c) 2000-2018 the FFmpeg
 developers
   built with gcc 7 (Ubuntu 7.2.0-8ubuntu3)
   configuration: --enable-libmp3lame --enable-libfdk-aac --enable-cuda
 --enable-cuvid --enable-nvenc --enable-nonfree --enable-libnpp --extra-
 cflags=-I/usr/local/cuda/include --extra-ldflags=-L/usr/local/cuda/lib64
   libavutil      56.  7.100 / 56.  7.100
   libavcodec     58. 10.100 / 58. 10.100
   libavformat    58.  9.100 / 58.  9.100
   libavdevice    58.  1.100 / 58.  1.100
   libavfilter     7. 11.101 /  7. 11.101
   libswscale      5.  0.101 /  5.  0.101
   libswresample   3.  0.101 /  3.  0.101
 [mpegts @ 0x5590806ca500] PES packet size mismatch
 Input #0, lavfi, from 'movie=1441_20180209070000.ts[out0+subcc]':
   Duration: N/A, start: 93886.435011, bitrate: N/A
     Stream #0:0: Video: rawvideo (I420 / 0x30323449), yuv420p, 1920x1080
 [SAR 1:1 DAR 16:9], 29.97 fps, 29.97 tbr, 90k tbn, 90k tbc
     Stream #0:1: Subtitle: eia_608
 Output #0, srt, to 'out2.srt':
   Metadata:
     encoder         : Lavf58.9.100
     Stream #0:0: Subtitle: subrip (srt)
     Metadata:
       encoder         : Lavc58.10.100 srt
 Stream mapping:
   Stream #0:1 -> #0:0 (eia_608 (cc_dec) -> subrip (srt))
 Press [q] to stop, [?] for help
 [Parsed_movie_0 @ 0x5590806ca000] EOF timestamp not reliable=7.99x
 size=      46kB time=00:27:44.26 bitrate=   0.2kbits/s speed=7.99x
 video:0kB audio:0kB subtitle:30kB other streams:0kB global headers:0kB
 muxing overhead: 50.277382%

 real    3m28.511s
 user    3m21.523s
 sys     0m5.121s
 }}}

 Compare to ccextractor on the same file:
 {{{
 % time ~/projects/ccextractor/linux/ccextractor 1441_20[21/1640$
 000.ts -o ~/out.srt
 CCExtractor 0.85, Carlos Fernandez Sanz, Volker Quetschke.
 Teletext portions taken from Petr Kutalek's telxcc
 --------------------------------------------------------------------------
 Input: 1441_20180209070000.ts
 [Extract: 1] [Stream mode: Autodetect]
 [Program : Auto ] [Hauppage mode: No] [Use MythTV code: Auto]
 [Timing mode: Auto] [Debug: No] [Buffer input: No]
 [Use pic_order_cnt_lsb for H.264: No] [Print CC decoder traces: No]
 [Target format: .srt] [Encoding: UTF-8] [Delay: 0] [Trim lines: No]
 [Add font color data: Yes] [Add font typesetting: Yes]
 [Convert case: No] [Video-edit join: No]
 [Extraction start time: not set (from start)]
 [Extraction end time: not set (to end)]
 [Live stream: No] [Clock frequency: 90000]
 [Teletext page: Autodetect]
 [Start credits text: None]

 -----------------------------------------------------------------
 Opening file: 1441_20180209070000.ts
 File seems to be a transport stream, enabling TS mode
 Analyzing data in general mode
 Creating /home/devesh/out.srt


 New video information found
 [1920 * 1080] [AR: 03 - 16:9] [FR: 04 - 29.97] [progressive: no]

   0%  |  00:00XDS Notice: Network call letters now KBCW
 XDS Notice: Network is now CW
 100%  |  29:58
 Number of NAL_type_7: 0
 Number of VCL_HRD: 0
 Number of NAL HRD: 0
 Number of jump-in-frames: 0
 Number of num_unexpected_sei_length: 0

 Total frames time:        00:29:59:030  (53917 frames at 29.97fps)

 Min PTS:                                26:04:46:368
 Max PTS:                                26:34:45:432
 Length:                          00:29:59:064

 Initial GOP time:          00:00:00:000
 Final GOP time:          00:00:00:000+30F
 Diff. GOP length:          00:00:00:000+30F     (00:00:01:001)


 Total user data fields: 53917
 HDTV type user data fields: 53917
 Done, processing time = 14 seconds
 Issues? Open a ticket here
 https://github.com/CCExtractor/ccextractor/issues

 real    0m13.910s
 user    0m9.021s
 sys     0m4.484s
 }}}

--
Ticket URL: <https://trac.ffmpeg.org/ticket/7018>
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