[Ffmpeg-devel] [BUG] problem ts demuxer h264 bbc

[Måns Rullgård]

Nico Sabbi <nicola_sabbi at fastwebnet.it> writes:

> M?ns Rullg?rd wrote:
>
>>Baptiste Coudurier <baptiste.coudurier at smartjog.com> writes:
>>
>>
>>>It works fine with mplayer with native ts demuxer though. When using
>>>-demuxer lavf, error appears again.
>>>
>>>
>>
>>That file is very badly broken.  What is labeled as an H.264 stream is
>>really an MPEG2 video stream and an H.264 stream interleaved.
>>
>>
>
> ??
> $ decode_pat  bbc-hd-test-mux.mpg
> libdvbpsi error (PSI decoder): TS discontinuity (received 1, expected
> 0) for PID 0
>
> New PAT
>   transport_stream_id : 1
>   version_number      : 1
>     | program_number @ [NIT|PMT]_PID
>     |              1 @ 0x258 (600)
>   active              : 1
>
> $ decode_pmt  bbc-hd-test-mux.mpg  1 600
> libdvbpsi error (PSI decoder): TS discontinuity (received 1, expected
> 0) for PID 600
>
> New active PMT
>   program_number : 1
>   version_number : 1
>   PCR_PID        : 0x5de (1502)
>     | type @ elementary_PID
>     | 0x1b (ISO/IEC 13818-1 reserved) @ 0x5de (1502)

Looks like decode_pmt needs an update to learn what stream type 0x1b is.

>     |  ] 0x52 : Component tag: 11
>     | 0x81 (User Private) @ 0x5e1 (1505)
>     |  ] 0x0a : "eng"
>     |  ] 0x6a : ""
>     |  ] 0x52 : Component tag: 8
>
> where do you see the mpeg2 video stream?

As I said, the PMT indicates an H.264 stream.  Extract this elementary
stream and feed it to an MPEG2 video parser:

sequence_header                          b3    
  horizontal_size_value                  2d0    720  
  vertical_size_value                    240    576  
  aspect_ratio_information               3      DAR=16/9
  frame_rate_code                        3      25 fps
  bit_rate_value                         4e20   20000
  marker_bit                             1     
  vbv_buffer_size_value                  70     112  
  constrained_parameters_flag            0     
  load_intra_quantiser_matrix            0     
  load_non_intra_quantiser_matrix        0     
extension_start_code                     b5    
sequence_extension                       1     
  profile_and_level_indication           48     Main profile @ Main level
  progressive_sequence                   1     
  chroma_format                          1      4:2:0
  horizontal_size_extension              0     
  vertical_size_extension                0     
  bit_rate_extension                     0     
  marker_bit                             1     
  vbv_buffer_size_extension              0     
  low_delay                              0     
  frame_rate_extension_n                 0     
  frame_rate_extension_d                 0     
extension_start_code                     b5    
sequence_display_extension               2     
  video_format                           1      PAL
  colour_description                     1     
    colour_primaries                     5      ITU-R BT.470-2 System B,G
    transfer_characteristics             5      ITU-R BT.470-2 System B,G
    matrix_coefficients                  5      ITU-R BT.470-2 System B,G
  display_horizontal_size                2d0    720  
  marker_bit                             1     
  display_vertical_size                  240    576  
group_of_pictures_header                 b8    
  time_code                              0     
    drop_frame_flag                      0     
    time_code_hours                      0     
    time_code_minutes                    0     
    marker_bit                           1     
    time_code_seconds                    0     
    time_code_pictures                   0     
  closed_gop                             1     
  broken_link                            0     
picture_header                           0     
  temporal_reference                     0     
  picture_coding_type                    1      I
  vbv_delay                              ffff  
  extra_bit_picture                      0     
extension_start_code                     b5    
picture_coding_extension                 8     
  f_code[0][0]                           f     
  f_code[0][1]                           f     
  f_code[1][0]                           f     
  f_code[1][1]                           f     
  intra_dc_precision                     1      9 bits
  picture_structure                      3      Frame picture
  top_field_first                        0     
  frame_pred_frame_dct                   1     
  concealment_motion_vectors             0     
  q_scale_type                           1     
  intra_vlc_format                       1     
  alternate_scan                         1     
  repeat_first_field                     0     
  chroma_420_type                        1     
  progressive_frame                      1     
  composite_display_flag                 0     
slice                                    1     
slice                                    61    
slice                                    3     
slice                                    4     

This looks like a perfectly normal MPEG2 video stream, except for that
0x61 slice start code, which is not allowed there.  0x61 is however
the "start code" for an H.264 NAL unit of a non-IDR slice.  Skipping
to byte 0x8e7ab, we encounter this byte sequence (no H.264 parser to
hand):

0008e7a0  08 30 16 5b 02 00 00 00  01 09 10 00 00 00 01 67
0008e7b0  64 40 28 ac 53 b0 16 81  13 61 62 00 00 03 00 02
0008e7c0  00 00 03 00 65 28 00 00  00 01 68 fe 3c b0 00 00
0008e7d0  00 01 06 01 01 32 06 01  84 80 00 00 00 01 61 be

This is a perfectly valid H.264 SPS NAL unit, followed by PPS and SEI.

Convinced?

-- 
M?ns Rullg?rd
mru at inprovide.com