[FFmpeg-trac] #5092(avcodec:new): Field order wrong for DV HD

[FFmpeg]

#5092: Field order wrong for DV HD
------------------------------------+-----------------------------------
             Reporter:  Dan203      |                    Owner:
                 Type:  defect      |                   Status:  new
             Priority:  normal      |                Component:  avcodec
              Version:  git-master  |               Resolution:
             Keywords:  dvvideo     |               Blocked By:
             Blocking:              |  Reproduced by developer:  0
Analyzed by developer:  0           |
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Comment (by Aleksandr_Slobodeniuk):

 Replying to [comment:9 cehoyos]:
 > How did you test this?
 > I ask because FFmpeg correctly shows tff here on the console and
 correctly uses tff when using a deinterlacer (tested with yadif).

 By watching
 {{{
 AVFrame->interlaced_frame
 }}}
 and
 {{{
 AVFrame->top_field_first
 }}}
 in the debugger, and watching how they're filling in libavcodec/dvdec.c :

 {{{
 /* Determine the codec's sample_aspect ratio from the packet */
     vsc_pack = buf + 80 * 5 + 48 + 5;
     if (*vsc_pack == dv_video_control) {
         apt    = buf[4] & 0x07;
         is16_9 = (vsc_pack[2] & 0x07) == 0x02 ||
                  (!apt && (vsc_pack[2] & 0x07) == 0x07);
         ff_set_sar(avctx, s->sys->sar[is16_9]);
     }

     if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
         return ret;
     frame->interlaced_frame = 1;
     frame->top_field_first  = 0;

     /* Determine the codec's field order from the packet */
     if ( *vsc_pack == dv_video_control ) {
         frame->top_field_first = !(vsc_pack[3] & 0x40);
     }
 }}}


 The situation is strange, because SMPTE 370m and 314m tells about bit
 (vsc_pack[3] & 0x40), that:
 {{{
 FS: First/second field flag
 FS indicates a field which is delivered during the field one period.
 0 = Field 2 is delivered; 1 = Field 1 is delivered.

 FF FS Output field
 1  1  Field 1 and field 2 are output in this order (1,2 sequence)
 1  0  Field 2 and field 1 are output in this order (2,1 sequence)
 0  1  Field 1 is output twice
 0  0  Field 2 is output twice
 }}}
 same for both 1080 system and 720 system.

 This is actually not what ffmpeg does:
 {{{
 frame->top_field_first = !(vsc_pack[3] & 0x40);
 }}}
 but this code works correctly for dv sd files.

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Ticket URL: <https://trac.ffmpeg.org/ticket/5092#comment:11>
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