• Main Page
  • Related Pages
  • Modules
  • Data Structures
  • Files
  • File List
  • Globals

libavcodec/yop.c

Go to the documentation of this file.
00001 
00026 #include "libavutil/intreadwrite.h"
00027 
00028 #include "avcodec.h"
00029 #include "get_bits.h"
00030 
00031 typedef struct YopDecContext {
00032     AVFrame frame;
00033     AVCodecContext *avctx;
00034 
00035     int num_pal_colors;
00036     int first_color[2];
00037     int frame_data_length;
00038     int row_pos;
00039 
00040     uint8_t *low_nibble;
00041     uint8_t *srcptr;
00042     uint8_t *dstptr;
00043     uint8_t *dstbuf;
00044 } YopDecContext;
00045 
00046 // These tables are taken directly from:
00047 // http://wiki.multimedia.cx/index.php?title=Psygnosis_YOP
00048 
00055 static const uint8_t paint_lut[15][4] =
00056     {{1, 2, 3, 4}, {1, 2, 0, 3},
00057      {1, 2, 1, 3}, {1, 2, 2, 3},
00058      {1, 0, 2, 3}, {1, 0, 0, 2},
00059      {1, 0, 1, 2}, {1, 1, 2, 3},
00060      {0, 1, 2, 3}, {0, 1, 0, 2},
00061      {1, 1, 0, 2}, {0, 1, 1, 2},
00062      {0, 0, 1, 2}, {0, 0, 0, 1},
00063      {1, 1, 1, 2},
00064     };
00065 
00070 static const int8_t motion_vector[16][2] =
00071     {{-4, -4}, {-2, -4},
00072      { 0, -4}, { 2, -4},
00073      {-4, -2}, {-4,  0},
00074      {-3, -3}, {-1, -3},
00075      { 1, -3}, { 3, -3},
00076      {-3, -1}, {-2, -2},
00077      { 0, -2}, { 2, -2},
00078      { 4, -2}, {-2,  0},
00079     };
00080 
00081 static av_cold int yop_decode_init(AVCodecContext *avctx)
00082 {
00083     YopDecContext *s = avctx->priv_data;
00084     s->avctx = avctx;
00085 
00086     if (avctx->width & 1 || avctx->height & 1 ||
00087         avcodec_check_dimensions(avctx, avctx->width, avctx->height) < 0) {
00088         av_log(avctx, AV_LOG_ERROR, "YOP has invalid dimensions\n");
00089         return -1;
00090     }
00091 
00092     avctx->pix_fmt = PIX_FMT_PAL8;
00093 
00094     s->num_pal_colors = avctx->extradata[0];
00095     s->first_color[0] = avctx->extradata[1];
00096     s->first_color[1] = avctx->extradata[2];
00097 
00098     if (s->num_pal_colors + s->first_color[0] > 256 ||
00099         s->num_pal_colors + s->first_color[1] > 256) {
00100         av_log(avctx, AV_LOG_ERROR,
00101                "YOP: palette parameters invalid, header probably corrupt\n");
00102         return AVERROR_INVALIDDATA;
00103     }
00104 
00105     return 0;
00106 }
00107 
00108 static av_cold int yop_decode_close(AVCodecContext *avctx)
00109 {
00110     YopDecContext *s = avctx->priv_data;
00111     if (s->frame.data[0])
00112         avctx->release_buffer(avctx, &s->frame);
00113     return 0;
00114 }
00115 
00121 static void yop_paint_block(YopDecContext *s, int tag)
00122 {
00123     s->dstptr[0]                        = s->srcptr[0];
00124     s->dstptr[1]                        = s->srcptr[paint_lut[tag][0]];
00125     s->dstptr[s->frame.linesize[0]]     = s->srcptr[paint_lut[tag][1]];
00126     s->dstptr[s->frame.linesize[0] + 1] = s->srcptr[paint_lut[tag][2]];
00127 
00128     // The number of src bytes consumed is in the last part of the lut entry.
00129     s->srcptr += paint_lut[tag][3];
00130 }
00131 
00136 static int yop_copy_previous_block(YopDecContext *s, int copy_tag)
00137 {
00138     uint8_t *bufptr;
00139 
00140     // Calculate position for the copy source
00141     bufptr = s->dstptr + motion_vector[copy_tag][0] +
00142              s->frame.linesize[0] * motion_vector[copy_tag][1];
00143     if (bufptr < s->dstbuf) {
00144         av_log(s->avctx, AV_LOG_ERROR,
00145                "YOP: cannot decode, file probably corrupt\n");
00146         return AVERROR_INVALIDDATA;
00147     }
00148 
00149     s->dstptr[0]                        = bufptr[0];
00150     s->dstptr[1]                        = bufptr[1];
00151     s->dstptr[s->frame.linesize[0]]     = bufptr[s->frame.linesize[0]];
00152     s->dstptr[s->frame.linesize[0] + 1] = bufptr[s->frame.linesize[0] + 1];
00153 
00154     return 0;
00155 }
00156 
00161 static uint8_t yop_get_next_nibble(YopDecContext *s)
00162 {
00163     int ret;
00164 
00165     if (s->low_nibble) {
00166         ret           = *s->low_nibble & 0xf;
00167         s->low_nibble = NULL;
00168     }else {
00169         s->low_nibble = s->srcptr++;
00170         ret           = *s->low_nibble >> 4;
00171     }
00172     return ret;
00173 }
00174 
00178 static void yop_next_macroblock(YopDecContext *s)
00179 {
00180     // If we are advancing to the next row of macroblocks
00181     if (s->row_pos == s->frame.linesize[0] - 2) {
00182         s->dstptr  += s->frame.linesize[0];
00183         s->row_pos =  0;
00184     }else {
00185         s->row_pos += 2;
00186     }
00187     s->dstptr += 2;
00188 }
00189 
00190 static int yop_decode_frame(AVCodecContext *avctx, void *data, int *data_size,
00191                             AVPacket *avpkt)
00192 {
00193     YopDecContext *s = avctx->priv_data;
00194     int tag, firstcolor, is_odd_frame;
00195     int ret, i;
00196     uint32_t *palette;
00197 
00198     if (s->frame.data[0])
00199         avctx->release_buffer(avctx, &s->frame);
00200 
00201     ret = avctx->get_buffer(avctx, &s->frame);
00202     if (ret < 0) {
00203         av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
00204         return ret;
00205     }
00206 
00207     s->frame.linesize[0] = avctx->width;
00208 
00209     s->dstbuf     = s->frame.data[0];
00210     s->dstptr     = s->frame.data[0];
00211     s->srcptr     = avpkt->data + 4;
00212     s->row_pos    = 0;
00213     s->low_nibble = NULL;
00214 
00215     is_odd_frame = avpkt->data[0];
00216     firstcolor   = s->first_color[is_odd_frame];
00217     palette      = (uint32_t *)s->frame.data[1];
00218 
00219     for (i = 0; i < s->num_pal_colors; i++, s->srcptr += 3)
00220         palette[i + firstcolor] = (s->srcptr[0] << 18) |
00221                                   (s->srcptr[1] << 10) |
00222                                   (s->srcptr[2] << 2);
00223 
00224     s->frame.palette_has_changed = 1;
00225 
00226     while (s->dstptr - s->dstbuf <
00227            avctx->width * avctx->height &&
00228            s->srcptr - avpkt->data < avpkt->size) {
00229 
00230         tag = yop_get_next_nibble(s);
00231 
00232         if (tag != 0xf) {
00233             yop_paint_block(s, tag);
00234         }else {
00235             tag = yop_get_next_nibble(s);
00236             ret = yop_copy_previous_block(s, tag);
00237             if (ret < 0) {
00238                 avctx->release_buffer(avctx, &s->frame);
00239                 return ret;
00240             }
00241         }
00242         yop_next_macroblock(s);
00243     }
00244 
00245     *data_size        = sizeof(AVFrame);
00246     *(AVFrame *) data = s->frame;
00247     return avpkt->size;
00248 }
00249 
00250 AVCodec yop_decoder = {
00251     "yop",
00252     AVMEDIA_TYPE_VIDEO,
00253     CODEC_ID_YOP,
00254     sizeof(YopDecContext),
00255     yop_decode_init,
00256     NULL,
00257     yop_decode_close,
00258     yop_decode_frame,
00259     .long_name = NULL_IF_CONFIG_SMALL("Psygnosis YOP Video"),
00260 };

Generated on Fri Sep 16 2011 17:17:47 for FFmpeg by  doxygen 1.7.1