[FFmpeg-devel] [PATCH]yuv4mpeg: Do not set interlaced_frame

[Tim Nicholson]

On 29/01/13 09:18, Carl Eugen Hoyos wrote:
> Hi!
> 
> The documentation of interlaced_frame says that it should only be written by 
> libavcodec, the yuv4mpeg demuxer currently violates this.
> 
> Attached patch fixes this and changes the behaviour on damaged headers 
> slightly.
> 
> Please review, Carl Eugen
> 
> 
> patchyuv4mpeginterlaced.diff
> 
> 
> diff --git a/libavformat/yuv4mpeg.c b/libavformat/yuv4mpeg.c
> index ff039bd..0eaa48c 100644
> --- a/libavformat/yuv4mpeg.c
> +++ b/libavformat/yuv4mpeg.c
> @@ -58,6 +58,12 @@ static int yuv4_generate_header(AVFormatContext *s, char* buf)
>      inter = 'p'; /* progressive is the default */
>      if (st->codec->coded_frame && st->codec->coded_frame->interlaced_frame)
>          inter = st->codec->coded_frame->top_field_first ? 't' : 'b';
> +    if (st->codec->field_order > AV_FIELD_UNKNOWN)
> +        if (st->codec->field_order > AV_FIELD_PROGRESSIVE) {
> +            inter = st->codec->field_order == AV_FIELD_TT || st->codec->field_order == AV_FIELD_TB ? 't' : 'b';
> +        } else {
> +             inter = 'p';
> +        }
> 

So you are leaving the original as a fall back when
(st->codec->field_order == AV_FIELD_UNKNOWN ?


>      switch (st->codec->pix_fmt) {
>      case AV_PIX_FMT_GRAY8:
> @@ -319,7 +325,7 @@ static int yuv4_read_header(AVFormatContext *s)
>  {
>      char header[MAX_YUV4_HEADER + 10];  // Include headroom for
>                                          // the longest option
> -    char *tokstart, *tokend, *header_end;
> +    char *tokstart, *tokend, *header_end, interlaced = '?';
>      int i;
>      AVIOContext *pb = s->pb;
>      int width = -1, height  = -1, raten   = 0,
> @@ -425,28 +431,7 @@ static int yuv4_read_header(AVFormatContext *s)
>                  tokstart++;
>              break;
>          case 'I': // Interlace type
> -            switch (*tokstart++){
> -            case '?':
> -                break;
> -            case 'p':
> -                s1->interlaced_frame = 0;
> -                break;
> -            case 't':
> -                s1->interlaced_frame = 1;
> -                s1->top_field_first = 1;
> -                break;
> -            case 'b':
> -                s1->interlaced_frame = 1;
> -                s1->top_field_first = 0;
> -                break;
> -            case 'm':
> -                av_log(s, AV_LOG_ERROR, "YUV4MPEG stream contains mixed "
> -                       "interlaced and non-interlaced frames.\n");
> -                return -1;
> -            default:
> -                av_log(s, AV_LOG_ERROR, "YUV4MPEG has invalid header.\n");
> -                return -1;
> -            }
> +            interlaced = *tokstart++;
>              break;
>          case 'F': // Frame rate
>              sscanf(tokstart, "%d:%d", &raten, &rated); // 0:0 if unknown
> @@ -547,6 +532,27 @@ static int yuv4_read_header(AVFormatContext *s)
>      st->sample_aspect_ratio           = (AVRational){ aspectn, aspectd };
>      st->codec->chroma_sample_location = chroma_sample_location;
>  
> +    switch (interlaced){
> +    case 'p':
> +        st->codec->field_order = AV_FIELD_PROGRESSIVE;
> +        break;
> +    case 't':
> +        st->codec->field_order = AV_FIELD_TT;

I believe this should be AV_FIELD_TB

> +        break;
> +    case 'b':
> +        st->codec->field_order = AV_FIELD_BB;

and this  AV_FIELD_BT

The description of the flag values in qtff is not very clear, however
every mov file (apart from mjepg codec) that I have looked at uses TB
(0x09) for conventional top field first material, and BT (0x0E) for
bottom field first, such as DV.

It doesn't help that qtff talks about:-
Top displayed first, Bottom stored first etc etc leading to TB
which in ffmpeg is:-
Bottom coded first Top displayed first, leading to BT

> +        break;
> +    case 'm':
> +        av_log(s, AV_LOG_ERROR, "YUV4MPEG stream contains mixed "
> +               "interlaced and non-interlaced frames.\n");
> +    case '?':
> +        st->codec->field_order = AV_FIELD_UNKNOWN;
> +        break;
> +    default:
> +        av_log(s, AV_LOG_ERROR, "YUV4MPEG has invalid header.\n");
> +        st->codec->field_order = AV_FIELD_UNKNOWN;
> +    }
> +
>      return 0;
>  }
>  
> @@ -556,7 +562,6 @@ static int yuv4_read_packet(AVFormatContext *s, AVPacket *pkt)
>      char header[MAX_FRAME_HEADER+1];
>      int packet_size, width, height, ret;
>      AVStream *st = s->streams[0];
> -    struct frame_attributes *s1 = s->priv_data;
>  
>      for (i = 0; i < MAX_FRAME_HEADER; i++) {
>          header[i] = avio_r8(s->pb);
> @@ -588,11 +593,6 @@ static int yuv4_read_packet(AVFormatContext *s, AVPacket *pkt)
>      else if (ret != packet_size)
>          return s->pb->eof_reached ? AVERROR_EOF : AVERROR(EIO);
>  
> -    if (st->codec->coded_frame) {
> -        st->codec->coded_frame->interlaced_frame = s1->interlaced_frame;
> -        st->codec->coded_frame->top_field_first  = s1->top_field_first;
> -    }
> -
>      pkt->stream_index = 0;
>      return 0;
>  }
> [..]

-- 
Tim