On Mon, Feb 12, 2018 at 05:37:32AM +0900, Yusuke Nakamura wrote:
> 2018-02-11 23:37 GMT+09:00 Jan Ekström <jee...@gmail.com>:
>
> > From: Masaki Tanaka <maki.r...@gmail.com>
> >
> > Lets one receive the proper field order from pictures coded in
> > field picture mode, until now forcibly set to BFF.
> > ---
> > libavcodec/mpegvideo_parser.c | 16 +++++++++++++++-
> > 1 file changed, 15 insertions(+), 1 deletion(-)
> >
> > diff --git a/libavcodec/mpegvideo_parser.c b/libavcodec/mpegvideo_parser.c
> > index be240b6890..3406346a8b 100644
> > --- a/libavcodec/mpegvideo_parser.c
> > +++ b/libavcodec/mpegvideo_parser.c
> > @@ -41,7 +41,7 @@ static void mpegvideo_extract_headers(AVCodecParserContext
> > *s,
> > uint32_t start_code;
> > int frame_rate_index, ext_type, bytes_left;
> > int frame_rate_ext_n, frame_rate_ext_d;
> > - int top_field_first, repeat_first_field, progressive_frame;
> > + int picture_structure, top_field_first, repeat_first_field,
> > progressive_frame;
> > int horiz_size_ext, vert_size_ext, bit_rate_ext;
> > int did_set_size=0;
> > int set_dim_ret = 0;
> > @@ -51,6 +51,7 @@ static void mpegvideo_extract_headers(AVCodecParserContext
> > *s,
> > enum AVPixelFormat pix_fmt = AV_PIX_FMT_NONE;
> > //FIXME replace the crap with get_bits()
> > s->repeat_pict = 0;
> > + s->picture_structure = AV_PICTURE_STRUCTURE_UNKNOWN;
> >
> > while (buf < buf_end) {
> > start_code= -1;
> > @@ -114,6 +115,7 @@ static void
> > mpegvideo_extract_headers(AVCodecParserContext
> > *s,
> > break;
> > case 0x8: /* picture coding extension */
> > if (bytes_left >= 5) {
> > + picture_structure = buf[2] & 0x03;
> > top_field_first = buf[3] & (1 << 7);
> > repeat_first_field = buf[3] & (1 << 1);
> > progressive_frame = buf[4] & (1 << 7);
> > @@ -138,6 +140,18 @@ static void
> > mpegvideo_extract_headers(AVCodecParserContext
> > *s,
> > s->field_order = AV_FIELD_BB;
> > } else
> > s->field_order = AV_FIELD_PROGRESSIVE;
> > +
> > + switch (picture_structure) {
> > + case PICT_TOP_FIELD:
> > + s->picture_structure =
> > AV_PICTURE_STRUCTURE_TOP_FIELD;
> > + break;
> > + case PICT_BOTTOM_FIELD:
> > + s->picture_structure =
> > AV_PICTURE_STRUCTURE_BOTTOM_FIELD;
> > + break;
> > + case PICT_FRAME:
> > + s->picture_structure =
> > AV_PICTURE_STRUCTURE_FRAME;
> > + break;
> > + }
> >
>
> Libavcodec handles MPEG-2 Video packet per frame but not picture, and the
> parser stops immediately after parsing the first slice of the picture. So,
> the parser returns per full frame but picture_structure says it's a field
> picture. This is evil and this is the reason why I hesitate to post this
> patch. I'm interested in how other devs consider this evil solution. I
> think the parser should parse the second field too if encountering a field
> coded picture, and treat the packet as frame coded and set field_order
> appropriate.I think a better API is needed to export the picture_structure correctly. With the API here, i think unspecified is better than delcaring field pictures to be frames. The field value is also what decoders would use, they have to 2 field pics arent the same as a frame picture [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB In a rich man's house there is no place to spit but his face. -- Diogenes of Sinope
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