a64.c
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1 /*
2  * a64 muxer
3  * Copyright (c) 2009 Tobias Bindhammer
4  *
5  * This file is part of Libav.
6  *
7  * Libav is free software; you can redistribute it and/or
8  * modify it under the terms of the GNU Lesser General Public
9  * License as published by the Free Software Foundation; either
10  * version 2.1 of the License, or (at your option) any later version.
11  *
12  * Libav is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15  * Lesser General Public License for more details.
16  *
17  * You should have received a copy of the GNU Lesser General Public
18  * License along with Libav; if not, write to the Free Software
19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20  */
21 
22 #include "libavcodec/avcodec.h"
23 #include "libavcodec/a64enc.h"
24 #include "libavcodec/bytestream.h"
25 #include "avformat.h"
26 
27 typedef struct A64MuxerContext {
32 
33 static int a64_write_header(struct AVFormatContext *s)
34 {
35  AVCodecContext *avctx = s->streams[0]->codec;
36  A64MuxerContext *c = s->priv_data;
37  uint8_t header[5] = {
38  0x00, //load
39  0x40, //address
40  0x00, //mode
41  0x00, //charset_lifetime (multi only)
42  0x00 //fps in 50/fps;
43  };
44  c->interleaved = 0;
45  switch (avctx->codec->id) {
46  case CODEC_ID_A64_MULTI:
47  header[2] = 0x00;
48  header[3] = AV_RB32(avctx->extradata+0);
49  header[4] = 2;
50  break;
52  header[2] = 0x01;
53  header[3] = AV_RB32(avctx->extradata+0);
54  header[4] = 3;
55  break;
56  default:
57  return AVERROR(EINVAL);
58  }
59  avio_write(s->pb, header, 2);
60  c->prev_pkt.size = 0;
61  c->prev_frame_count = 0;
62  return 0;
63 }
64 
65 static int a64_write_packet(struct AVFormatContext *s, AVPacket *pkt)
66 {
67  AVCodecContext *avctx = s->streams[0]->codec;
68  A64MuxerContext *c = s->priv_data;
69  int i, j;
70  int ch_chunksize;
71  int lifetime;
72  int frame_count;
73  int charset_size;
74  int frame_size;
75  int num_frames;
76 
77  /* fetch values from extradata */
78  switch (avctx->codec->id) {
79  case CODEC_ID_A64_MULTI:
81  if(c->interleaved) {
82  /* Write interleaved, means we insert chunks of the future charset before each current frame.
83  * Reason: if we load 1 charset + corresponding frames in one block on c64, we need to store
84  * them first and then display frame by frame to keep in sync. Thus we would read and write
85  * the data for colram from/to ram first and waste too much time. If we interleave and send the
86  * charset beforehand, we assemble a new charset chunk by chunk, write current screen data to
87  * screen-ram to be displayed and decode the colram directly to colram-location $d800 during
88  * the overscan, while reading directly from source.
89  * This is the only way so far, to achieve 25fps on c64 */
90  if(avctx->extradata) {
91  /* fetch values from extradata */
92  lifetime = AV_RB32(avctx->extradata + 0);
93  frame_count = AV_RB32(avctx->extradata + 4);
94  charset_size = AV_RB32(avctx->extradata + 8);
95  frame_size = AV_RB32(avctx->extradata + 12);
96 
97  /* TODO: sanity checks? */
98  } else {
99  av_log(avctx, AV_LOG_ERROR, "extradata not set\n");
100  return AVERROR(EINVAL);
101  }
102 
103  ch_chunksize=charset_size/lifetime;
104  /* TODO: check if charset/size is % lifetime, but maybe check in codec */
105 
106  if(pkt->data) num_frames = lifetime;
107  else num_frames = c->prev_frame_count;
108 
109  for(i = 0; i < num_frames; i++) {
110  if(pkt->data) {
111  /* if available, put newest charset chunk into buffer */
112  avio_write(s->pb, pkt->data + ch_chunksize * i, ch_chunksize);
113  } else {
114  /* a bit ugly, but is there an alternative to put many zeros? */
115  for(j = 0; j < ch_chunksize; j++) avio_w8(s->pb, 0);
116  }
117 
118  if(c->prev_pkt.data) {
119  /* put frame (screen + colram) from last packet into buffer */
120  avio_write(s->pb, c->prev_pkt.data + charset_size + frame_size * i, frame_size);
121  } else {
122  /* a bit ugly, but is there an alternative to put many zeros? */
123  for(j = 0; j < frame_size; j++) avio_w8(s->pb, 0);
124  }
125  }
126 
127  /* backup current packet for next turn */
128  if(pkt->data) {
129  /* no backup packet yet? create one! */
130  if(!c->prev_pkt.data) av_new_packet(&c->prev_pkt, pkt->size);
131  /* we have a packet and data is big enough, reuse it */
132  if(c->prev_pkt.data && c->prev_pkt.size >= pkt->size) {
133  memcpy(c->prev_pkt.data, pkt->data, pkt->size);
134  c->prev_pkt.size = pkt->size;
135  } else {
136  av_log(avctx, AV_LOG_ERROR, "Too less memory for prev_pkt.\n");
137  return AVERROR(ENOMEM);
138  }
139  }
140 
142  break;
143  }
144  default:
145  /* Write things as is. Nice for self-contained frames from non-multicolor modes or if played
146  * directly from ram and not from a streaming device (rrnet/mmc) */
147  if(pkt) avio_write(s->pb, pkt->data, pkt->size);
148  break;
149  }
150 
151  avio_flush(s->pb);
152  return 0;
153 }
154 
155 static int a64_write_trailer(struct AVFormatContext *s)
156 {
157  A64MuxerContext *c = s->priv_data;
158  AVPacket pkt = {0};
159  /* need to flush last packet? */
160  if(c->interleaved) a64_write_packet(s, &pkt);
161  /* discard backed up packet */
163  return 0;
164 }
165 
167  .name = "a64",
168  .long_name = NULL_IF_CONFIG_SMALL("a64 - video for Commodore 64"),
169  .extensions = "a64, A64",
170  .priv_data_size = sizeof (A64Context),
171  .video_codec = CODEC_ID_A64_MULTI,
175 };