Opened 11 months ago

Closed 8 weeks ago

#7018 closed defect (needs_more_info)

cc_dec decoder very slow at extracting CEA-708 closed captions from mpeg2ts file

Reported by: devesh Owned by:
Priority: normal Component: undetermined
Version: git-master Keywords:
Cc: Blocked By:
Blocking: Reproduced by developer: no
Analyzed by developer: no


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]"
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 '':          
    encoder         : Lavf58.9.100      
    Stream #0:0: Subtitle: subrip (srt) 
      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 ~/                                                             
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/           

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

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

Change History (1)

comment:1 Changed 8 weeks ago by cehoyos

  • Component changed from avcodec to undetermined
  • Keywords cc_dec CEA-708 captions performance removed
  • Resolution set to needs_more_info
  • Status changed from new to closed

May be the same issue as #7542.

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