[FFmpeg-devel] [PATCH v1 3/3] avformat/rtpdec_rfc4175: handle interlace format

[Rostislav Pehlivanov]

On 10 April 2018 at 22:21, Patrick Keroulas <
patrick.keroulas at savoirfairelinux.com> wrote:

> From: Damien Riegel <damien.riegel at savoirfairelinux.com>
>
> In order to handle the interlaced formats, the demuxer has only a few
> things to do:
>  - parse the SDP correctly and propagate the information
>  - check the field bit in the RFC4175 header, and pass that information
>    to the decoder
>
> In interlaced mode, received data only consist of fields, and their
> heights are half of the frame size, so some adjustments must be done
> here and there to take that into account.
>
> Signed-off-by: Damien Riegel <damien.riegel at savoirfairelinux.com>
> ---
>  libavformat/rtpdec_rfc4175.c | 23 +++++++++++++++++++++--
>  1 file changed, 21 insertions(+), 2 deletions(-)
>
> diff --git a/libavformat/rtpdec_rfc4175.c b/libavformat/rtpdec_rfc4175.c
> index e9c62c1..55a36eb 100644
> --- a/libavformat/rtpdec_rfc4175.c
> +++ b/libavformat/rtpdec_rfc4175.c
> @@ -31,6 +31,8 @@ struct PayloadContext {
>      int depth;
>      int width;
>      int height;
> +    int interlaced;
> +    int field;
>
>      uint8_t *frame;
>      unsigned int frame_size;
> @@ -65,10 +67,18 @@ static int rfc4175_parse_format(AVStream *stream,
> PayloadContext *data)
>          return AVERROR_INVALIDDATA;
>      }
>
> +    if (data->interlaced)
> +        stream->codecpar->field_order = AV_FIELD_TT;
> +    else
> +        stream->codecpar->field_order = AV_FIELD_PROGRESSIVE;
> +
>      stream->codecpar->format = pixfmt;
>      stream->codecpar->codec_tag = tag;
>      stream->codecpar->bits_per_coded_sample = bits_per_sample;
> -    data->frame_size = data->width * data->height * data->pgroup /
> data->xinc;
> +    if (data->interlaced)
> +        data->frame_size = data->width * (data->height / 2) *
> data->pgroup / data->xinc;
> +    else
> +        data->frame_size = data->width * data->height * data->pgroup /
> data->xinc;
>
>      return 0;
>  }
> @@ -85,6 +95,8 @@ static int rfc4175_parse_fmtp(AVFormatContext *s,
> AVStream *stream,
>          data->sampling = av_strdup(value);
>      else if (!strncmp(attr, "depth", 5))
>          data->depth = atoi(value);
> +    else if (!strncmp(attr, "interlace", 9))
> +        data->interlaced = 1;
>
>      return 0;
>  }
> @@ -131,7 +143,11 @@ static int rfc4175_finalize_packet(PayloadContext
> *data, AVPacket *pkt,
>         av_freep(&data->frame);
>     }
>
> +   /* In the packet header, the field is set to 0 for top field
> +    * and 1 for bottom */
> +   pkt->flags |= data->field ? 0 : AV_PKT_FLAG_TOP_FIELD;
>     data->frame = NULL;
> +   data->field = 0;
>
>     return ret;
>  }
> @@ -141,7 +157,7 @@ static int rfc4175_handle_packet(AVFormatContext
> *ctx, PayloadContext *data,
>                                   const uint8_t * buf, int len,
>                                   uint16_t seq, int flags)
>  {
> -    int length, line, offset, cont;
> +    int length, line, offset, cont, field;
>      const uint8_t *headers = buf + 2; /* skip extended seqnum */
>      const uint8_t *payload = buf + 2;
>      int payload_len = len - 2;
> @@ -194,11 +210,14 @@ static int rfc4175_handle_packet(AVFormatContext
> *ctx, PayloadContext *data,
>              return AVERROR_INVALIDDATA;
>
>          length = (headers[0] << 8) | headers[1];
> +        field = (headers[2] & 0x80);
>          line = ((headers[2] & 0x7f) << 8) | headers[3];
>          offset = ((headers[4] & 0x7f) << 8) | headers[5];
>          cont = headers[4] & 0x80;
>          headers += 6;
>
> +        data->field = field;
> +
>          if (length % data->pgroup)
>              return AVERROR_INVALIDDATA;
>
> --
> 2.7.4
>
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>


Needs to use the bottom field packet flag too.