[FFmpeg-trac] #1656(undetermined:new): AVRn (mjpeg): change field order for ntsc

[FFmpeg]

#1656: AVRn (mjpeg): change field order for ntsc
-------------------------------------+-------------------------------------
               Reporter:  ami_stuff  |                  Owner:
                   Type:  defect     |                 Status:  new
               Priority:  normal     |              Component:
                Version:             |  undetermined
  unspecified                        |               Keywords:
             Blocked By:             |               Blocking:
Reproduced by developer:  0          |  Analyzed by developer:  0
-------------------------------------+-------------------------------------
 AVRn in ntsc mode needs change of field order, so probably check for MKTAG
 and "NTSC" string in the file should be aded.

 libavcodec/mjpegdec.c:

 {{{
 av_cold int ff_mjpeg_decode_init(AVCodecContext *avctx)
 {
     MJpegDecodeContext *s = avctx->priv_data;

     if (!s->picture_ptr)
         s->picture_ptr = &s->picture;
     avcodec_get_frame_defaults(&s->picture);


     s->avctx = avctx;
     ff_dsputil_init(&s->dsp, avctx);
     ff_init_scantable(s->dsp.idct_permutation, &s->scantable,
 ff_zigzag_direct);
     s->buffer_size   = 0;
     s->buffer        = NULL;
     s->start_code    = -1;
     s->first_picture = 1;
     s->org_height    = avctx->coded_height;
     avctx->chroma_sample_location = AVCHROMA_LOC_CENTER;

     build_basic_mjpeg_vlc(s);

     if (s->extern_huff) {
         av_log(avctx, AV_LOG_INFO, "using external huffman table\n");
         init_get_bits(&s->gb, avctx->extradata, avctx->extradata_size *
 8);
         if (ff_mjpeg_decode_dht(s)) {
             av_log(avctx, AV_LOG_ERROR,
                    "error using external huffman table, switching back to
 internal\n");
             build_basic_mjpeg_vlc(s);
         }
     }
 -    if (avctx->field_order == AV_FIELD_BB) {
 +    if (avctx->field_order == AV_FIELD_BB || s->avctx->codec_tag ==
 MKTAG('A', 'V', 'R', 'n') && ntsc_string) {
         s->interlace_polarity = 1;           /* bottom field first */
         av_log(avctx, AV_LOG_DEBUG, "bottom field first\n");
     }
     if (avctx->codec->id == CODEC_ID_AMV)
         s->flipped = 1;

     return 0;
 }
 }}}

 {{{
 C:\>ffmpeg -i ntsc.avi out.bmp
 ffmpeg version N-43678-gceb8773 Copyright (c) 2000-2012 the FFmpeg
 developers
   built on Aug 18 2012 02:22:03 with gcc 4.5.0 (GCC) 20100414 (Fedora
 MinGW 4.5.
 0-1.fc14)
   configuration: --prefix=/var/www/users/research/ffmpeg/snapshots/build
 --arch=
 x86 --target-os=mingw32 --cross-prefix=i686-pc-mingw32- --cc='ccache i686
 -pc-min
 gw32-gcc' --enable-w32threads --enable-memalign-hack --enable-runtime-
 cpudetect
 --enable-cross-compile --enable-static --disable-shared --extra-
 libs='-lws2_32 -
 lwinmm -lpthread' --extra-cflags='--static
 -I/var/www/users/research/ffmpeg/snap
 shots/build/include' --extra-ldflags='-static
 -L/var/www/users/research/ffmpeg/s
 napshots/build/lib' --enable-bzlib --enable-zlib --enable-gpl --enable-
 version3
 --enable-nonfree --enable-libx264 --enable-libspeex --enable-libtheora
 --enable-
 libvorbis --enable-libfaac --enable-libxvid --enable-libopencore-amrnb
 --enable-
 libopencore-amrwb --enable-libmp3lame --enable-libvpx --disable-
 decoder=libvpx
   libavutil      51. 70.100 / 51. 70.100
   libavcodec     54. 53.100 / 54. 53.100
   libavformat    54. 25.100 / 54. 25.100
   libavdevice    54.  2.100 / 54.  2.100
   libavfilter     3. 10.100 /  3. 10.100
   libswscale      2.  1.101 /  2.  1.101
   libswresample   0. 15.100 /  0. 15.100
   libpostproc    52.  0.100 / 52.  0.100
 Input #0, avi, from 'ntsc.avi':
   Duration: 00:00:00.10, start: 0.000000, bitrate: 6630 kb/s
     Stream #0:0: Video: mjpeg (AVRn / 0x6E525641), yuvj422p, 720x496, 10
 tbr, 10
  tbn, 10 tbc
 Output #0, image2, to 'out.bmp':
   Metadata:
     encoder         : Lavf54.25.100
     Stream #0:0: Video: bmp, bgr24, 720x496, q=2-31, 200 kb/s, 90k tbn, 10
 tbc
 Stream mapping:
   Stream #0:0 -> #0:0 (mjpeg -> bmp)
 Press [q] to stop, [?] for help
 frame=    1 fps=0.0 q=0.0 Lsize=       0kB time=00:00:00.10 bitrate=
 0.0kbits/
 s
 video:1046kB audio:0kB subtitle:0 global headers:0kB muxing overhead
 -100.000000
 %
 }}}

-- 
Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/1656>
FFmpeg <http://ffmpeg.org>
FFmpeg issue tracker