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 "libavutil/avassert.h"
26 #include "libavutil/crc.h"
27 #include "libavutil/intreadwrite.h"
28 #include "libavutil/log.h"
29 #include "libavutil/opt.h"
30 #include "libavcodec/apng.h"
31 #include "libavcodec/png.h"
32 
33 typedef struct APNGMuxContext {
34     AVClass *class;
35 
36     uint32_t plays;
37     AVRational last_delay;
38 
39     uint64_t acTL_offset;
40     uint32_t frame_number;
41 
42     AVPacket *prev_packet;
43     AVRational prev_delay;
44 
45     int framerate_warned;
46 
47     uint8_t *extra_data;
48     int extra_data_size;
49 } APNGMuxContext;
50 
apng_find_chunk(uint32_t tag, const uint8_t *buf, size_t length)51 static const uint8_t *apng_find_chunk(uint32_t tag, const uint8_t *buf,
52                                       size_t length)
53 {
54     size_t b;
55     for (b = 0; AV_RB32(buf + b) + 12ULL <= length - b; b += AV_RB32(buf + b) + 12ULL)
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 > UINT16_MAX || apng->last_delay.den > UINT16_MAX) {
95         av_reduce(&apng->last_delay.num, &apng->last_delay.den,
96                   apng->last_delay.num, apng->last_delay.den, UINT16_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     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         const uint8_t *existing_acTL_chunk;
139         const 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             const 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             const 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         const uint8_t *data, *data_end;
164         const uint8_t *existing_fcTL_chunk;
165 
166         if (apng->frame_number == 0) {
167             const uint8_t *existing_acTL_chunk;
168 
169             // Write normal PNG headers
170             avio_write(io_context, apng->extra_data, apng->extra_data_size);
171 
172             existing_acTL_chunk = apng_find_chunk(MKBETAG('a', 'c', 'T', 'L'), apng->extra_data, apng->extra_data_size);
173             if (!existing_acTL_chunk) {
174                 uint8_t buf[8];
175                 // Write animation control header
176                 apng->acTL_offset = avio_tell(io_context);
177                 AV_WB32(buf, UINT_MAX); // number of frames (filled in later)
178                 AV_WB32(buf + 4, apng->plays);
179                 apng_write_chunk(io_context, MKBETAG('a', 'c', 'T', 'L'), buf, 8);
180             }
181         }
182 
183         data     = apng->prev_packet->data;
184         data_end = data + apng->prev_packet->size;
185         existing_fcTL_chunk = apng_find_chunk(MKBETAG('f', 'c', 'T', 'L'), apng->prev_packet->data, apng->prev_packet->size);
186         if (existing_fcTL_chunk) {
187             AVRational delay;
188 
189             if (AV_RB32(existing_fcTL_chunk) != APNG_FCTL_CHUNK_SIZE)
190                 return AVERROR_INVALIDDATA;
191 
192             existing_fcTL_chunk += 8;
193             delay.num = AV_RB16(existing_fcTL_chunk + 20);
194             delay.den = AV_RB16(existing_fcTL_chunk + 22);
195 
196             if (delay.num == 0 && delay.den == 0) {
197                 uint8_t new_fcTL_chunk[APNG_FCTL_CHUNK_SIZE];
198 
199                 if (packet) {
200                     int64_t delay_num_raw = (packet->dts - apng->prev_packet->dts) * codec_stream->time_base.num;
201                     int64_t delay_den_raw = codec_stream->time_base.den;
202                     if (!av_reduce(&delay.num, &delay.den, delay_num_raw, delay_den_raw, UINT16_MAX) &&
203                         !apng->framerate_warned) {
204                         av_log(format_context, AV_LOG_WARNING,
205                                "Frame rate is too high or specified too precisely. Unable to copy losslessly.\n");
206                         apng->framerate_warned = 1;
207                     }
208                 } else if (apng->last_delay.num > 0) {
209                     delay = apng->last_delay;
210                 } else {
211                     delay = apng->prev_delay;
212                 }
213 
214                 avio_write(io_context, data, (existing_fcTL_chunk - 8) - data);
215                 data = existing_fcTL_chunk + APNG_FCTL_CHUNK_SIZE + 4 /* CRC-32 */;
216                 // Update frame control header with new delay
217                 memcpy(new_fcTL_chunk, existing_fcTL_chunk, sizeof(new_fcTL_chunk));
218                 AV_WB16(new_fcTL_chunk + 20, delay.num);
219                 AV_WB16(new_fcTL_chunk + 22, delay.den);
220                 apng_write_chunk(io_context, MKBETAG('f', 'c', 'T', 'L'),
221                                  new_fcTL_chunk, sizeof(new_fcTL_chunk));
222             }
223             apng->prev_delay = delay;
224         }
225 
226         // Write frame data
227         avio_write(io_context, data, data_end - data);
228     }
229     ++apng->frame_number;
230 
231     av_packet_unref(apng->prev_packet);
232     if (packet)
233         av_packet_ref(apng->prev_packet, packet);
234     return 0;
235 }
236 
apng_write_packet(AVFormatContext *format_context, AVPacket *packet)237 static int apng_write_packet(AVFormatContext *format_context, AVPacket *packet)
238 {
239     APNGMuxContext *apng = format_context->priv_data;
240     int ret;
241 
242     if (!apng->prev_packet) {
243         apng->prev_packet = av_packet_alloc();
244         if (!apng->prev_packet)
245             return AVERROR(ENOMEM);
246 
247         av_packet_ref(apng->prev_packet, packet);
248     } else {
249         ret = flush_packet(format_context, packet);
250         if (ret < 0)
251             return ret;
252     }
253 
254     return 0;
255 }
256 
apng_write_trailer(AVFormatContext *format_context)257 static int apng_write_trailer(AVFormatContext *format_context)
258 {
259     APNGMuxContext *apng = format_context->priv_data;
260     AVIOContext *io_context = format_context->pb;
261     uint8_t buf[8];
262     int ret;
263 
264     if (apng->prev_packet) {
265         ret = flush_packet(format_context, NULL);
266         if (ret < 0)
267             return ret;
268     }
269 
270     apng_write_chunk(io_context, MKBETAG('I', 'E', 'N', 'D'), NULL, 0);
271 
272     if (apng->acTL_offset && (io_context->seekable & AVIO_SEEKABLE_NORMAL)) {
273         avio_seek(io_context, apng->acTL_offset, SEEK_SET);
274 
275         AV_WB32(buf, apng->frame_number);
276         AV_WB32(buf + 4, apng->plays);
277         apng_write_chunk(io_context, MKBETAG('a', 'c', 'T', 'L'), buf, 8);
278     }
279 
280     return 0;
281 }
282 
apng_deinit(AVFormatContext *s)283 static void apng_deinit(AVFormatContext *s)
284 {
285     APNGMuxContext *apng = s->priv_data;
286 
287     av_packet_free(&apng->prev_packet);
288     av_freep(&apng->extra_data);
289     apng->extra_data_size = 0;
290 }
291 
292 #define OFFSET(x) offsetof(APNGMuxContext, x)
293 #define ENC AV_OPT_FLAG_ENCODING_PARAM
294 static const AVOption options[] = {
295     { "plays", "Number of times to play the output: 0 - infinite loop, 1 - no loop", OFFSET(plays),
296       AV_OPT_TYPE_INT, { .i64 = 1 }, 0, UINT16_MAX, ENC },
297     { "final_delay", "Force delay after the last frame", OFFSET(last_delay),
298       AV_OPT_TYPE_RATIONAL, { .dbl = 0 }, 0, UINT16_MAX, ENC },
299     { NULL },
300 };
301 
302 static const AVClass apng_muxer_class = {
303     .class_name = "APNG muxer",
304     .item_name  = av_default_item_name,
305     .version    = LIBAVUTIL_VERSION_INT,
306     .option     = options,
307 };
308 
309 const AVOutputFormat ff_apng_muxer = {
310     .name           = "apng",
311     .long_name      = NULL_IF_CONFIG_SMALL("Animated Portable Network Graphics"),
312     .mime_type      = "image/png",
313     .extensions     = "apng",
314     .priv_data_size = sizeof(APNGMuxContext),
315     .audio_codec    = AV_CODEC_ID_NONE,
316     .video_codec    = AV_CODEC_ID_APNG,
317     .write_header   = apng_write_header,
318     .write_packet   = apng_write_packet,
319     .write_trailer  = apng_write_trailer,
320     .deinit         = apng_deinit,
321     .priv_class     = &apng_muxer_class,
322     .flags          = AVFMT_VARIABLE_FPS,
323 };
324