FFmpeg
 All Data Structures Namespaces Files Functions Variables Typedefs Enumerations Enumerator Macros Groups Pages
cpia.c
Go to the documentation of this file.
1 /*
2  * CPiA video decoder.
3  * Copyright (c) 2010 Hans de Goede <hdegoede@redhat.com>
4  *
5  * This decoder is based on the LGPL code available at
6  * https://v4l4j.googlecode.com/svn/v4l4j/trunk/libvideo/libv4lconvert/cpia1.c
7  *
8  * This file is part of FFmpeg.
9  *
10  * FFmpeg is free software; you can redistribute it and/or
11  * modify it under the terms of the GNU Lesser General Public
12  * License as published by the Free Software Foundation; either
13  * version 2.1 of the License, or (at your option) any later version.
14  *
15  * FFmpeg is distributed in the hope that it will be useful,
16  * but WITHOUT ANY WARRANTY; without even the implied warranty of
17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
18  * Lesser General Public License for more details.
19  *
20  * You should have received a copy of the GNU Lesser General Public
21  * License along with FFmpeg; if not, write to the Free Software
22  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
23  */
24 
25 #include "avcodec.h"
26 #include "get_bits.h"
27 #include "internal.h"
28 
29 
30 #define FRAME_HEADER_SIZE 64
31 #define MAGIC_0 0x19 /**< First header byte */
32 #define MAGIC_1 0x68 /**< Second header byte */
33 #define SUBSAMPLE_420 0
34 #define SUBSAMPLE_422 1
35 #define YUVORDER_YUYV 0
36 #define YUVORDER_UYVY 1
37 #define NOT_COMPRESSED 0
38 #define COMPRESSED 1
39 #define NO_DECIMATION 0
40 #define DECIMATION_ENAB 1
41 #define EOL 0xfd /**< End Of Line marker */
42 #define EOI 0xff /**< End Of Image marker */
43 
44 
45 typedef struct {
47 } CpiaContext;
48 
49 
51  void *data, int *got_frame, AVPacket* avpkt)
52 {
53  CpiaContext* const cpia = avctx->priv_data;
54  int i,j,ret;
55 
56  uint8_t* const header = avpkt->data;
57  uint8_t* src;
58  int src_size;
59  uint16_t linelength;
60  uint8_t skip;
61 
62  AVFrame *frame = cpia->frame;
63  uint8_t *y, *u, *v, *y_end, *u_end, *v_end;
64 
65  // Check header
66  if ( avpkt->size < FRAME_HEADER_SIZE
67  || header[0] != MAGIC_0 || header[1] != MAGIC_1
68  || (header[17] != SUBSAMPLE_420 && header[17] != SUBSAMPLE_422)
69  || (header[18] != YUVORDER_YUYV && header[18] != YUVORDER_UYVY)
70  || (header[28] != NOT_COMPRESSED && header[28] != COMPRESSED)
71  || (header[29] != NO_DECIMATION && header[29] != DECIMATION_ENAB)
72  ) {
73  av_log(avctx, AV_LOG_ERROR, "Invalid header!\n");
74  return AVERROR_INVALIDDATA;
75  }
76 
77  // currently unsupported properties
78  if (header[17] == SUBSAMPLE_422) {
79  av_log(avctx, AV_LOG_ERROR, "Unsupported subsample!\n");
80  return AVERROR_PATCHWELCOME;
81  }
82  if (header[18] == YUVORDER_UYVY) {
83  av_log(avctx, AV_LOG_ERROR, "Unsupported YUV byte order!\n");
84  return AVERROR_PATCHWELCOME;
85  }
86  if (header[29] == DECIMATION_ENAB) {
87  av_log(avctx, AV_LOG_ERROR, "Decimation unsupported!\n");
88  return AVERROR_PATCHWELCOME;
89  }
90 
91  src = header + FRAME_HEADER_SIZE;
92  src_size = avpkt->size - FRAME_HEADER_SIZE;
93 
94  if (header[28] == NOT_COMPRESSED) {
96  frame->key_frame = 1;
97  } else {
99  frame->key_frame = 0;
100  }
101 
102  // Get buffer filled with previous frame
103  if ((ret = ff_reget_buffer(avctx, frame)) < 0)
104  return ret;
105 
106 
107  for ( i = 0;
108  i < frame->height;
109  i++, src += linelength, src_size -= linelength
110  ) {
111  // Read line length, two byte little endian
112  linelength = AV_RL16(src);
113  src += 2;
114 
115  if (src_size < linelength) {
117  av_log(avctx, AV_LOG_WARNING, "Frame ended enexpectedly!\n");
118  break;
119  }
120  if (src[linelength - 1] != EOL) {
122  av_log(avctx, AV_LOG_WARNING, "Wrong line length %d or line not terminated properly (found 0x%02x)!\n", linelength, src[linelength - 1]);
123  break;
124  }
125 
126  /* Update the data pointers. Y data is on every line.
127  * U and V data on every second line
128  */
129  y = &frame->data[0][i * frame->linesize[0]];
130  u = &frame->data[1][(i >> 1) * frame->linesize[1]];
131  v = &frame->data[2][(i >> 1) * frame->linesize[2]];
132  y_end = y + frame->linesize[0] - 1;
133  u_end = u + frame->linesize[1] - 1;
134  v_end = v + frame->linesize[2] - 1;
135 
136  if ((i & 1) && header[17] == SUBSAMPLE_420) {
137  /* We are on a odd line and 420 subsample is used.
138  * On this line only Y values are specified, one per pixel.
139  */
140  for (j = 0; j < linelength - 1; j++) {
141  if (y > y_end) {
143  av_log(avctx, AV_LOG_WARNING, "Decoded data exceeded linesize!\n");
144  break;
145  }
146  if ((src[j] & 1) && header[28] == COMPRESSED) {
147  /* It seems that odd lines are always uncompressed, but
148  * we do it according to specification anyways.
149  */
150  skip = src[j] >> 1;
151  y += skip;
152  } else {
153  *(y++) = src[j];
154  }
155  }
156  } else if (header[17] == SUBSAMPLE_420) {
157  /* We are on an even line and 420 subsample is used.
158  * On this line each pair of pixels is described by four bytes.
159  */
160  for (j = 0; j < linelength - 4; ) {
161  if (y + 1 > y_end || u > u_end || v > v_end) {
163  av_log(avctx, AV_LOG_WARNING, "Decoded data exceeded linesize!\n");
164  break;
165  }
166  if ((src[j] & 1) && header[28] == COMPRESSED) {
167  // Skip amount of pixels and move forward one byte
168  skip = src[j] >> 1;
169  y += skip;
170  u += skip >> 1;
171  v += skip >> 1;
172  j++;
173  } else {
174  // Set image data as specified and move forward 4 bytes
175  *(y++) = src[j];
176  *(u++) = src[j+1];
177  *(y++) = src[j+2];
178  *(v++) = src[j+3];
179  j += 4;
180  }
181  }
182  }
183  }
184 
185  *got_frame = 1;
186  if ((ret = av_frame_ref(data, cpia->frame)) < 0)
187  return ret;
188 
189  return avpkt->size;
190 }
191 
193 {
194  CpiaContext *s = avctx->priv_data;
195 
196  // output pixel format
197  avctx->pix_fmt = AV_PIX_FMT_YUV420P;
198 
199  /* The default timebase set by the v4l2 demuxer leads to probing which is buggy.
200  * Set some reasonable time_base to skip this.
201  */
202  if (avctx->time_base.num == 1 && avctx->time_base.den == 1000000) {
203  avctx->time_base.num = 1;
204  avctx->time_base.den = 60;
205  }
206 
207  s->frame = av_frame_alloc();
208  if (!s->frame)
209  return AVERROR(ENOMEM);
210 
211  return 0;
212 }
213 
215 {
216  CpiaContext *s = avctx->priv_data;
217 
218  av_frame_free(&s->frame);
219 
220  return 0;
221 }
222 
224  .name = "cpia",
225  .long_name = NULL_IF_CONFIG_SMALL("CPiA video format"),
226  .type = AVMEDIA_TYPE_VIDEO,
227  .id = AV_CODEC_ID_CPIA,
228  .priv_data_size = sizeof(CpiaContext),
232  .capabilities = CODEC_CAP_DR1,
233 };