/*
  * CPiA video decoder.
  * Copyright (c) 2010 Hans de Goede <hdegoede@redhat.com>
  *
  * This decoder is based on the LGPL code available at
  * https://v4l4j.googlecode.com/svn/v4l4j/trunk/libvideo/libv4lconvert/cpia1.c
  *
  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2.1 of the License, or (at your option) any later version.
  *
  * FFmpeg is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public
  * License along with FFmpeg; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
 #include "avcodec.h"
 #include "get_bits.h"
 
 
 #define FRAME_HEADER_SIZE 64
 #define MAGIC_0         0x19    /**< First header byte */
 #define MAGIC_1         0x68    /**< Second header byte */
 #define SUBSAMPLE_420      0
 #define SUBSAMPLE_422      1
 #define YUVORDER_YUYV      0
 #define YUVORDER_UYVY      1
 #define NOT_COMPRESSED     0
 #define COMPRESSED         1
 #define NO_DECIMATION      0
 #define DECIMATION_ENAB    1
 #define EOL             0xfd    /**< End Of Line marker */
 #define EOI             0xff    /**< End Of Image marker */
 
 
 typedef struct {
     AVFrame frame;
 } CpiaContext;
 
 

 static int cpia_decode_frame(AVCodecContext *avctx,
                              void *data, int *got_frame, AVPacket* avpkt)

 {
     CpiaContext* const cpia = avctx->priv_data;
     int i,j,ret;
 
     uint8_t* const header = avpkt->data;
     uint8_t* src;
     int src_size;
     uint16_t linelength;
     uint8_t skip;
 
     AVFrame* const frame = &cpia->frame;
     uint8_t *y, *u, *v, *y_end, *u_end, *v_end;
 
     // Check header
     if ( avpkt->size < FRAME_HEADER_SIZE
       || header[0] != MAGIC_0 || header[1] != MAGIC_1
       || (header[17] != SUBSAMPLE_420 && header[17] != SUBSAMPLE_422)
       || (header[18] != YUVORDER_YUYV && header[18] != YUVORDER_UYVY)
       || (header[28] != NOT_COMPRESSED && header[28] != COMPRESSED)
       || (header[29] != NO_DECIMATION && header[29] != DECIMATION_ENAB)
     ) {
         av_log(avctx, AV_LOG_ERROR, "Invalid header!\n");
         return AVERROR_INVALIDDATA;
     }
 
     // currently unsupported properties
     if (header[17] == SUBSAMPLE_422) {
         av_log(avctx, AV_LOG_ERROR, "Unsupported subsample!\n");
         return AVERROR_PATCHWELCOME;
     }
     if (header[18] == YUVORDER_UYVY) {
         av_log(avctx, AV_LOG_ERROR, "Unsupported YUV byte order!\n");
         return AVERROR_PATCHWELCOME;
     }
     if (header[29] == DECIMATION_ENAB) {
         av_log(avctx, AV_LOG_ERROR, "Decimation unsupported!\n");
         return AVERROR_PATCHWELCOME;
     }
 
     src = header + FRAME_HEADER_SIZE;
     src_size = avpkt->size - FRAME_HEADER_SIZE;
 
     if (header[28] == NOT_COMPRESSED) {
         frame->pict_type = AV_PICTURE_TYPE_I;
         frame->key_frame = 1;
     } else {
         frame->pict_type = AV_PICTURE_TYPE_P;
         frame->key_frame = 0;
     }
 

     // Get buffer filled with previous frame
     if ((ret = avctx->reget_buffer(avctx, frame)) < 0) {
         av_log(avctx, AV_LOG_ERROR, "reget_buffer() failed!\n");
         return ret;
     }
 

 
     for ( i = 0;
           i < frame->height;
           i++, src += linelength, src_size -= linelength
     ) {
         // Read line length, two byte little endian
         linelength = AV_RL16(src);
         src += 2;
 
         if (src_size < linelength) {

             av_frame_set_decode_error_flags(frame, FF_DECODE_ERROR_INVALID_BITSTREAM);

             av_log(avctx, AV_LOG_WARNING, "Frame ended enexpectedly!\n");
             break;
         }
         if (src[linelength - 1] != EOL) {

             av_frame_set_decode_error_flags(frame, FF_DECODE_ERROR_INVALID_BITSTREAM);

             av_log(avctx, AV_LOG_WARNING, "Wrong line length %d or line not terminated properly (found 0x%02x)!\n", linelength, src[linelength - 1]);
             break;
         }
 
         /* Update the data pointers. Y data is on every line.
          * U and V data on every second line
          */
         y = &frame->data[0][i * frame->linesize[0]];
         u = &frame->data[1][(i >> 1) * frame->linesize[1]];
         v = &frame->data[2][(i >> 1) * frame->linesize[2]];
         y_end = y + frame->linesize[0] - 1;
         u_end = u + frame->linesize[1] - 1;
         v_end = v + frame->linesize[2] - 1;
 
         if ((i & 1) && header[17] == SUBSAMPLE_420) {
             /* We are on a odd line and 420 subsample is used.
              * On this line only Y values are specified, one per pixel.
              */
             for (j = 0; j < linelength - 1; j++) {
                 if (y > y_end) {

                     av_frame_set_decode_error_flags(frame, FF_DECODE_ERROR_INVALID_BITSTREAM);

                     av_log(avctx, AV_LOG_WARNING, "Decoded data exceeded linesize!\n");
                     break;
                 }
                 if ((src[j] & 1) && header[28] == COMPRESSED) {
                     /* It seems that odd lines are always uncompressed, but
                      * we do it according to specification anyways.
                      */
                     skip = src[j] >> 1;
                     y += skip;
                 } else {
                     *(y++) = src[j];
                 }
             }
         } else if (header[17] == SUBSAMPLE_420) {
             /* We are on an even line and 420 subsample is used.
              * On this line each pair of pixels is described by four bytes.
              */
             for (j = 0; j < linelength - 4; ) {
                 if (y + 1 > y_end || u > u_end || v > v_end) {

                     av_frame_set_decode_error_flags(frame, FF_DECODE_ERROR_INVALID_BITSTREAM);

                     av_log(avctx, AV_LOG_WARNING, "Decoded data exceeded linesize!\n");
                     break;
                 }
                 if ((src[j] & 1) && header[28] == COMPRESSED) {
                     // Skip amount of pixels and move forward one byte
                     skip = src[j] >> 1;
                     y += skip;
                     u += skip >> 1;
                     v += skip >> 1;
                     j++;
                 } else {
                     // Set image data as specified and move forward 4 bytes
                     *(y++) = src[j];
                     *(u++) = src[j+1];
                     *(y++) = src[j+2];
                     *(v++) = src[j+3];
                     j += 4;
                 }
             }
         }
     }
 

     *got_frame = 1;

     *(AVFrame*) data = *frame;
 
     return avpkt->size;
 }
 
 static av_cold int cpia_decode_init(AVCodecContext *avctx)
 {
     // output pixel format

     avctx->pix_fmt = AV_PIX_FMT_YUV420P;

 
     /* The default timebase set by the v4l2 demuxer leads to probing which is buggy.
      * Set some reasonable time_base to skip this.
      */
     if (avctx->time_base.num == 1 && avctx->time_base.den == 1000000) {
         avctx->time_base.num = 1;
         avctx->time_base.den = 60;
     }
 
     return 0;
 }
 
 
 AVCodec ff_cpia_decoder = {
     .name           = "cpia",
     .type           = AVMEDIA_TYPE_VIDEO,
     .id             = AV_CODEC_ID_CPIA,
     .priv_data_size = sizeof(CpiaContext),
     .init           = cpia_decode_init,
     .decode         = cpia_decode_frame,
     .capabilities   = CODEC_CAP_DR1,
     .long_name      = NULL_IF_CONFIG_SMALL("CPiA video format"),
 };