1 /*
2 * APNG muxer
3 * Copyright (c) 2015 Donny Yang
4 *
5 * first version by Donny Yang <work@kota.moe>
6 *
7 * This file is part of FFmpeg.
8 *
9 * FFmpeg is free software; you can redistribute it and/or
10 * modify it under the terms of the GNU Lesser General Public
11 * License as published by the Free Software Foundation; either
12 * version 2.1 of the License, or (at your option) any later version.
13 *
14 * FFmpeg is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
17 * Lesser General Public License for more details.
18 *
19 * You should have received a copy of the GNU Lesser General Public
20 * License along with FFmpeg; if not, write to the Free Software
21 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
22 */
23
24 #include "avformat.h"
25 #include "internal.h"
26 #include "libavutil/avassert.h"
27 #include "libavutil/crc.h"
28 #include "libavutil/intreadwrite.h"
29 #include "libavutil/log.h"
30 #include "libavutil/opt.h"
31 #include "libavcodec/png.h"
32 #include "libavcodec/apng.h"
33
34 typedef struct APNGMuxContext {
35 AVClass *class;
36
37 uint32_t plays;
38 AVRational last_delay;
39
40 uint64_t acTL_offset;
41 uint32_t frame_number;
42
43 AVPacket *prev_packet;
44 AVRational prev_delay;
45
46 int framerate_warned;
47
48 uint8_t *extra_data;
49 int extra_data_size;
50 } APNGMuxContext;
51
apng_find_chunk(uint32_t tag,uint8_t * buf,size_t length)52 static uint8_t *apng_find_chunk(uint32_t tag, uint8_t *buf, size_t length)
53 {
54 size_t b;
55 for (b = 0; b < length; b += AV_RB32(buf + b) + 12)
56 if (AV_RB32(&buf[b + 4]) == tag)
57 return &buf[b];
58 return NULL;
59 }
60
apng_write_chunk(AVIOContext * io_context,uint32_t tag,uint8_t * buf,size_t length)61 static void apng_write_chunk(AVIOContext *io_context, uint32_t tag,
62 uint8_t *buf, size_t length)
63 {
64 const AVCRC *crc_table = av_crc_get_table(AV_CRC_32_IEEE_LE);
65 uint32_t crc = ~0U;
66 uint8_t tagbuf[4];
67
68 av_assert0(crc_table);
69
70 avio_wb32(io_context, length);
71 AV_WB32(tagbuf, tag);
72 crc = av_crc(crc_table, crc, tagbuf, 4);
73 avio_wb32(io_context, tag);
74 if (length > 0) {
75 crc = av_crc(crc_table, crc, buf, length);
76 avio_write(io_context, buf, length);
77 }
78 avio_wb32(io_context, ~crc);
79 }
80
apng_write_header(AVFormatContext * format_context)81 static int apng_write_header(AVFormatContext *format_context)
82 {
83 APNGMuxContext *apng = format_context->priv_data;
84 AVCodecParameters *par = format_context->streams[0]->codecpar;
85
86 if (format_context->nb_streams != 1 ||
87 format_context->streams[0]->codecpar->codec_type != AVMEDIA_TYPE_VIDEO ||
88 format_context->streams[0]->codecpar->codec_id != AV_CODEC_ID_APNG) {
89 av_log(format_context, AV_LOG_ERROR,
90 "APNG muxer supports only a single video APNG stream.\n");
91 return AVERROR(EINVAL);
92 }
93
94 if (apng->last_delay.num > USHRT_MAX || apng->last_delay.den > USHRT_MAX) {
95 av_reduce(&apng->last_delay.num, &apng->last_delay.den,
96 apng->last_delay.num, apng->last_delay.den, USHRT_MAX);
97 av_log(format_context, AV_LOG_WARNING,
98 "Last frame delay is too precise. Reducing to %d/%d (%f).\n",
99 apng->last_delay.num, apng->last_delay.den, (double)apng->last_delay.num / apng->last_delay.den);
100 }
101
102 avio_wb64(format_context->pb, PNGSIG);
103 // Remaining headers are written when they are copied from the encoder
104
105 if (par->extradata_size) {
106 apng->extra_data = av_mallocz(par->extradata_size + AV_INPUT_BUFFER_PADDING_SIZE);
107 if (!apng->extra_data)
108 return AVERROR(ENOMEM);
109 apng->extra_data_size = par->extradata_size;
110 memcpy(apng->extra_data, par->extradata, par->extradata_size);
111 }
112
113 return 0;
114 }
115
flush_packet(AVFormatContext * format_context,AVPacket * packet)116 static int flush_packet(AVFormatContext *format_context, AVPacket *packet)
117 {
118 APNGMuxContext *apng = format_context->priv_data;
119 AVIOContext *io_context = format_context->pb;
120 AVStream *codec_stream = format_context->streams[0];
121 uint8_t *side_data = NULL;
122 buffer_size_t side_data_size;
123
124 av_assert0(apng->prev_packet);
125
126 side_data = av_packet_get_side_data(apng->prev_packet, AV_PKT_DATA_NEW_EXTRADATA, &side_data_size);
127
128 if (side_data_size) {
129 av_freep(&apng->extra_data);
130 apng->extra_data = av_mallocz(side_data_size + AV_INPUT_BUFFER_PADDING_SIZE);
131 if (!apng->extra_data)
132 return AVERROR(ENOMEM);
133 apng->extra_data_size = side_data_size;
134 memcpy(apng->extra_data, side_data, apng->extra_data_size);
135 }
136
137 if (apng->frame_number == 0 && !packet) {
138 uint8_t *existing_acTL_chunk;
139 uint8_t *existing_fcTL_chunk;
140
141 av_log(format_context, AV_LOG_INFO, "Only a single frame so saving as a normal PNG.\n");
142
143 // Write normal PNG headers without acTL chunk
144 existing_acTL_chunk = apng_find_chunk(MKBETAG('a', 'c', 'T', 'L'), apng->extra_data, apng->extra_data_size);
145 if (existing_acTL_chunk) {
146 uint8_t *chunk_after_acTL = existing_acTL_chunk + AV_RB32(existing_acTL_chunk) + 12;
147 avio_write(io_context, apng->extra_data, existing_acTL_chunk - apng->extra_data);
148 avio_write(io_context, chunk_after_acTL, apng->extra_data + apng->extra_data_size - chunk_after_acTL);
149 } else {
150 avio_write(io_context, apng->extra_data, apng->extra_data_size);
151 }
152
153 // Write frame data without fcTL chunk
154 existing_fcTL_chunk = apng_find_chunk(MKBETAG('f', 'c', 'T', 'L'), apng->prev_packet->data, apng->prev_packet->size);
155 if (existing_fcTL_chunk) {
156 uint8_t *chunk_after_fcTL = existing_fcTL_chunk + AV_RB32(existing_fcTL_chunk) + 12;
157 avio_write(io_context, apng->prev_packet->data, existing_fcTL_chunk - apng->prev_packet->data);
158 avio_write(io_context, chunk_after_fcTL, apng->prev_packet->data + apng->prev_packet->size - chunk_after_fcTL);
159 } else {
160 avio_write(io_context, apng->prev_packet->data, apng->prev_packet->size);
161 }
162 } else {
163 uint8_t *existing_fcTL_chunk;
164
165 if (apng->frame_number == 0) {
166 uint8_t *existing_acTL_chunk;
167
168 // Write normal PNG headers
169 avio_write(io_context, apng->extra_data, apng->extra_data_size);
170
171 existing_acTL_chunk = apng_find_chunk(MKBETAG('a', 'c', 'T', 'L'), apng->extra_data, apng->extra_data_size);
172 if (!existing_acTL_chunk) {
173 uint8_t buf[8];
174 // Write animation control header
175 apng->acTL_offset = avio_tell(io_context);
176 AV_WB32(buf, UINT_MAX); // number of frames (filled in later)
177 AV_WB32(buf + 4, apng->plays);
178 apng_write_chunk(io_context, MKBETAG('a', 'c', 'T', 'L'), buf, 8);
179 }
180 }
181
182 existing_fcTL_chunk = apng_find_chunk(MKBETAG('f', 'c', 'T', 'L'), apng->prev_packet->data, apng->prev_packet->size);
183 if (existing_fcTL_chunk) {
184 AVRational delay;
185
186 existing_fcTL_chunk += 8;
187 delay.num = AV_RB16(existing_fcTL_chunk + 20);
188 delay.den = AV_RB16(existing_fcTL_chunk + 22);
189
190 if (delay.num == 0 && delay.den == 0) {
191 if (packet) {
192 int64_t delay_num_raw = (packet->dts - apng->prev_packet->dts) * codec_stream->time_base.num;
193 int64_t delay_den_raw = codec_stream->time_base.den;
194 if (!av_reduce(&delay.num, &delay.den, delay_num_raw, delay_den_raw, USHRT_MAX) &&
195 !apng->framerate_warned) {
196 av_log(format_context, AV_LOG_WARNING,
197 "Frame rate is too high or specified too precisely. Unable to copy losslessly.\n");
198 apng->framerate_warned = 1;
199 }
200 } else if (apng->last_delay.num > 0) {
201 delay = apng->last_delay;
202 } else {
203 delay = apng->prev_delay;
204 }
205
206 // Update frame control header with new delay
207 AV_WB16(existing_fcTL_chunk + 20, delay.num);
208 AV_WB16(existing_fcTL_chunk + 22, delay.den);
209 AV_WB32(existing_fcTL_chunk + 26, ~av_crc(av_crc_get_table(AV_CRC_32_IEEE_LE), ~0U, existing_fcTL_chunk - 4, 26 + 4));
210 }
211 apng->prev_delay = delay;
212 }
213
214 // Write frame data
215 avio_write(io_context, apng->prev_packet->data, apng->prev_packet->size);
216 }
217 ++apng->frame_number;
218
219 av_packet_unref(apng->prev_packet);
220 if (packet)
221 av_packet_ref(apng->prev_packet, packet);
222 return 0;
223 }
224
apng_write_packet(AVFormatContext * format_context,AVPacket * packet)225 static int apng_write_packet(AVFormatContext *format_context, AVPacket *packet)
226 {
227 APNGMuxContext *apng = format_context->priv_data;
228 int ret;
229
230 if (!apng->prev_packet) {
231 apng->prev_packet = av_packet_alloc();
232 if (!apng->prev_packet)
233 return AVERROR(ENOMEM);
234
235 av_packet_ref(apng->prev_packet, packet);
236 } else {
237 ret = flush_packet(format_context, packet);
238 if (ret < 0)
239 return ret;
240 }
241
242 return 0;
243 }
244
apng_write_trailer(AVFormatContext * format_context)245 static int apng_write_trailer(AVFormatContext *format_context)
246 {
247 APNGMuxContext *apng = format_context->priv_data;
248 AVIOContext *io_context = format_context->pb;
249 uint8_t buf[8];
250 int ret;
251
252 if (apng->prev_packet) {
253 ret = flush_packet(format_context, NULL);
254 if (ret < 0)
255 return ret;
256 }
257
258 apng_write_chunk(io_context, MKBETAG('I', 'E', 'N', 'D'), NULL, 0);
259
260 if (apng->acTL_offset && (io_context->seekable & AVIO_SEEKABLE_NORMAL)) {
261 avio_seek(io_context, apng->acTL_offset, SEEK_SET);
262
263 AV_WB32(buf, apng->frame_number);
264 AV_WB32(buf + 4, apng->plays);
265 apng_write_chunk(io_context, MKBETAG('a', 'c', 'T', 'L'), buf, 8);
266 }
267
268 return 0;
269 }
270
apng_deinit(AVFormatContext * s)271 static void apng_deinit(AVFormatContext *s)
272 {
273 APNGMuxContext *apng = s->priv_data;
274
275 av_packet_free(&apng->prev_packet);
276 av_freep(&apng->extra_data);
277 apng->extra_data_size = 0;
278 }
279
280 #define OFFSET(x) offsetof(APNGMuxContext, x)
281 #define ENC AV_OPT_FLAG_ENCODING_PARAM
282 static const AVOption options[] = {
283 { "plays", "Number of times to play the output: 0 - infinite loop, 1 - no loop", OFFSET(plays),
284 AV_OPT_TYPE_INT, { .i64 = 1 }, 0, UINT_MAX, ENC },
285 { "final_delay", "Force delay after the last frame", OFFSET(last_delay),
286 AV_OPT_TYPE_RATIONAL, { .dbl = 0 }, 0, USHRT_MAX, ENC },
287 { NULL },
288 };
289
290 static const AVClass apng_muxer_class = {
291 .class_name = "APNG muxer",
292 .item_name = av_default_item_name,
293 .version = LIBAVUTIL_VERSION_INT,
294 .option = options,
295 };
296
297 AVOutputFormat ff_apng_muxer = {
298 .name = "apng",
299 .long_name = NULL_IF_CONFIG_SMALL("Animated Portable Network Graphics"),
300 .mime_type = "image/png",
301 .extensions = "apng",
302 .priv_data_size = sizeof(APNGMuxContext),
303 .audio_codec = AV_CODEC_ID_NONE,
304 .video_codec = AV_CODEC_ID_APNG,
305 .write_header = apng_write_header,
306 .write_packet = apng_write_packet,
307 .write_trailer = apng_write_trailer,
308 .deinit = apng_deinit,
309 .priv_class = &apng_muxer_class,
310 .flags = AVFMT_VARIABLE_FPS,
311 };
312