[FFmpeg-trac] #10012(avcodec:new): rkmppdec improperly judging interlaced source

[FFmpeg]

#10012: rkmppdec improperly judging interlaced source
-------------------------------------+-----------------------------------
             Reporter:  tc           |                    Owner:  (none)
                 Type:  defect       |                   Status:  new
             Priority:  normal       |                Component:  avcodec
              Version:  unspecified  |               Resolution:
             Keywords:  interlaced   |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-----------------------------------
Description changed by tc:

Old description:

> Summary of the bug:
>
> https://github.com/FFmpeg/FFmpeg/blob/master/libavcodec/rkmppdec.c#L407
>
> {{{#!c
> frame->interlaced_frame = ((mode & MPP_FRAME_FLAG_FIELD_ORDER_MASK) ==
> MPP_FRAME_FLAG_DEINTERLACED);
> }}}
>
> my understanding of frame->interlaced is that it should be non-zero when
> input frames are interlaced.
> `mpp_frame_get_mode(mppframe)` returns a bitfield covered by
> `mpp_frame.h`:
>
> {{{#!c
> #define MPP_FRAME_FLAG_TOP_FIELD        (0x00000001)
> /* bottom field only */
> #define MPP_FRAME_FLAG_BOT_FIELD        (0x00000002)
> /* paired field */
> #define MPP_FRAME_FLAG_PAIRED_FIELD
> (MPP_FRAME_FLAG_TOP_FIELD|MPP_FRAME_FLAG_BOT_FIELD)
> /* paired field with field order of top first */
> #define MPP_FRAME_FLAG_TOP_FIRST        (0x00000004)
> /* paired field with field order of bottom first */
> #define MPP_FRAME_FLAG_BOT_FIRST        (0x00000008)
> /* paired field with unknown field order (MBAFF) */
> #define MPP_FRAME_FLAG_DEINTERLACED
> (MPP_FRAME_FLAG_TOP_FIRST|MPP_FRAME_FLAG_BOT_FIRST)
> #define MPP_FRAME_FLAG_FIELD_ORDER_MASK (0x0000000C)
> }}}
>
> For a typical tff interlaced source, returned mode is `0x7` (`0b111`).
> For bff, it would be `0b1011`.
>
> However, MPP_FRAME_FLAG_DEINTERLACED masks both TFF and BFF, which is
> impossible in interlaced sources.
> As per discussion here: https://github.com/JeffyCN/FFmpeg/issues/10
>
> the correct logic would be inverse of current, i.e.
>
> {{{#!c
> frame->interlaced_frame = (!((mode & MPP_FRAME_FLAG_FIELD_ORDER_MASK) ==
> MPP_FRAME_FLAG_DEINTERLACED));
> }}}
>
> After making this change, the stream is properly marked as interlaced:
> {{{
> Stream #0:0: Video: h264, drm_prime(bt709, top coded first (swapped)),
> 1440x1080, q=2-31, 3000 kb/s, 29.97 fps, 90k tbn
> }}}

New description:

 Summary of the bug:

 https://github.com/FFmpeg/FFmpeg/blob/master/libavcodec/rkmppdec.c#L407

 {{{#!c
 frame->interlaced_frame = ((mode & MPP_FRAME_FLAG_FIELD_ORDER_MASK) ==
 MPP_FRAME_FLAG_DEINTERLACED);
 }}}

 my understanding of frame->interlaced is that it should be non-zero when
 input frames are interlaced.
 `mpp_frame_get_mode(mppframe)` returns a bitfield covered by
 `mpp_frame.h`:

 {{{#!c
 #define MPP_FRAME_FLAG_TOP_FIELD        (0x00000001)
 /* bottom field only */
 #define MPP_FRAME_FLAG_BOT_FIELD        (0x00000002)
 /* paired field */
 #define MPP_FRAME_FLAG_PAIRED_FIELD
 (MPP_FRAME_FLAG_TOP_FIELD|MPP_FRAME_FLAG_BOT_FIELD)
 /* paired field with field order of top first */
 #define MPP_FRAME_FLAG_TOP_FIRST        (0x00000004)
 /* paired field with field order of bottom first */
 #define MPP_FRAME_FLAG_BOT_FIRST        (0x00000008)
 /* paired field with unknown field order (MBAFF) */
 #define MPP_FRAME_FLAG_DEINTERLACED
 (MPP_FRAME_FLAG_TOP_FIRST|MPP_FRAME_FLAG_BOT_FIRST)
 #define MPP_FRAME_FLAG_FIELD_ORDER_MASK (0x0000000C)
 }}}

 For a typical tff interlaced source, returned mode is `0x7` (`0b111`). For
 bff, it would be `0b1011`.

 However, MPP_FRAME_FLAG_DEINTERLACED masks both TFF and BFF, which is
 impossible in interlaced sources.
 As per discussion here: https://github.com/JeffyCN/FFmpeg/issues/10

 the correct logic would be inverse of current, i.e.

 {{{#!c
 frame->interlaced_frame = (mode & MPP_FRAME_FLAG_FIELD_ORDER_MASK);
 }}}

 After making this change, the stream is properly marked as interlaced:
 {{{
 Stream #0:0: Video: h264, drm_prime(bt709, top coded first (swapped)),
 1440x1080, q=2-31, 3000 kb/s, 29.97 fps, 90k tbn
 }}}

--
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/10012#comment:1>
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