aboutsummaryrefslogtreecommitdiffstats
path: root/libavformat/apngenc.c
blob: 0c40be297fcb83be31e91be6b5d54d5d3ba9ef9c (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
/*
 * APNG muxer
 * Copyright (c) 2015 Donny Yang
 *
 * first version by Donny Yang <work@kota.moe>
 *
 * 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 "avformat.h"
#include "internal.h"
#include "libavutil/avassert.h"
#include "libavutil/crc.h"
#include "libavutil/intreadwrite.h"
#include "libavutil/log.h"
#include "libavutil/opt.h"
#include "libavcodec/png.h"
#include "libavcodec/apng.h"

typedef struct APNGMuxContext {
    AVClass *class;

    uint32_t plays;
    AVRational last_delay;

    uint64_t acTL_offset;
    uint32_t frame_number;

    AVPacket *prev_packet;
    AVRational prev_delay;

    int framerate_warned;

    uint8_t *extra_data;
    int extra_data_size;
} APNGMuxContext;

static uint8_t *apng_find_chunk(uint32_t tag, uint8_t *buf, size_t length)
{
    size_t b;
    for (b = 0; b < length; b += AV_RB32(buf + b) + 12)
        if (AV_RB32(&buf[b + 4]) == tag)
            return &buf[b];
    return NULL;
}

static void apng_write_chunk(AVIOContext *io_context, uint32_t tag,
                             uint8_t *buf, size_t length)
{
    const AVCRC *crc_table = av_crc_get_table(AV_CRC_32_IEEE_LE);
    uint32_t crc = ~0U;
    uint8_t tagbuf[4];

    av_assert0(crc_table);

    avio_wb32(io_context, length);
    AV_WB32(tagbuf, tag);
    crc = av_crc(crc_table, crc, tagbuf, 4);
    avio_wb32(io_context, tag);
    if (length > 0) {
        crc = av_crc(crc_table, crc, buf, length);
        avio_write(io_context, buf, length);
    }
    avio_wb32(io_context, ~crc);
}

static int apng_write_header(AVFormatContext *format_context)
{
    APNGMuxContext *apng = format_context->priv_data;
    AVCodecParameters *par = format_context->streams[0]->codecpar;

    if (format_context->nb_streams != 1 ||
        format_context->streams[0]->codecpar->codec_type != AVMEDIA_TYPE_VIDEO ||
        format_context->streams[0]->codecpar->codec_id   != AV_CODEC_ID_APNG) {
        av_log(format_context, AV_LOG_ERROR,
               "APNG muxer supports only a single video APNG stream.\n");
        return AVERROR(EINVAL);
    }

    if (apng->last_delay.num > USHRT_MAX || apng->last_delay.den > USHRT_MAX) {
        av_reduce(&apng->last_delay.num, &apng->last_delay.den,
                  apng->last_delay.num, apng->last_delay.den, USHRT_MAX);
        av_log(format_context, AV_LOG_WARNING,
               "Last frame delay is too precise. Reducing to %d/%d (%f).\n",
               apng->last_delay.num, apng->last_delay.den, (double)apng->last_delay.num / apng->last_delay.den);
    }

    avio_wb64(format_context->pb, PNGSIG);
    // Remaining headers are written when they are copied from the encoder

    if (par->extradata_size) {
        apng->extra_data = av_mallocz(par->extradata_size + AV_INPUT_BUFFER_PADDING_SIZE);
        if (!apng->extra_data)
            return AVERROR(ENOMEM);
        apng->extra_data_size = par->extradata_size;
        memcpy(apng->extra_data, par->extradata, par->extradata_size);
    }

    return 0;
}

static int flush_packet(AVFormatContext *format_context, AVPacket *packet)
{
    APNGMuxContext *apng = format_context->priv_data;
    AVIOContext *io_context = format_context->pb;
    AVStream *codec_stream = format_context->streams[0];
    uint8_t *side_data = NULL;
    int side_data_size = 0;

    av_assert0(apng->prev_packet);

    side_data = av_packet_get_side_data(apng->prev_packet, AV_PKT_DATA_NEW_EXTRADATA, &side_data_size);

    if (side_data_size) {
        av_freep(&apng->extra_data);
        apng->extra_data = av_mallocz(side_data_size + AV_INPUT_BUFFER_PADDING_SIZE);
        if (!apng->extra_data)
            return AVERROR(ENOMEM);
        apng->extra_data_size = side_data_size;
        memcpy(apng->extra_data, side_data, apng->extra_data_size);
    }

    if (apng->frame_number == 0 && !packet) {
        uint8_t *existing_acTL_chunk;
        uint8_t *existing_fcTL_chunk;

        av_log(format_context, AV_LOG_INFO, "Only a single frame so saving as a normal PNG.\n");

        // Write normal PNG headers without acTL chunk
        existing_acTL_chunk = apng_find_chunk(MKBETAG('a', 'c', 'T', 'L'), apng->extra_data, apng->extra_data_size);
        if (existing_acTL_chunk) {
            uint8_t *chunk_after_acTL = existing_acTL_chunk + AV_RB32(existing_acTL_chunk) + 12;
            avio_write(io_context, apng->extra_data, existing_acTL_chunk - apng->extra_data);
            avio_write(io_context, chunk_after_acTL, apng->extra_data + apng->extra_data_size - chunk_after_acTL);
        } else {
            avio_write(io_context, apng->extra_data, apng->extra_data_size);
        }

        // Write frame data without fcTL chunk
        existing_fcTL_chunk = apng_find_chunk(MKBETAG('f', 'c', 'T', 'L'), apng->prev_packet->data, apng->prev_packet->size);
        if (existing_fcTL_chunk) {
            uint8_t *chunk_after_fcTL = existing_fcTL_chunk + AV_RB32(existing_fcTL_chunk) + 12;
            avio_write(io_context, apng->prev_packet->data, existing_fcTL_chunk - apng->prev_packet->data);
            avio_write(io_context, chunk_after_fcTL, apng->prev_packet->data + apng->prev_packet->size - chunk_after_fcTL);
        } else {
            avio_write(io_context, apng->prev_packet->data, apng->prev_packet->size);
        }
    } else {
        uint8_t *existing_fcTL_chunk;

        if (apng->frame_number == 0) {
            uint8_t *existing_acTL_chunk;

            // Write normal PNG headers
            avio_write(io_context, apng->extra_data, apng->extra_data_size);

            existing_acTL_chunk = apng_find_chunk(MKBETAG('a', 'c', 'T', 'L'), apng->extra_data, apng->extra_data_size);
            if (!existing_acTL_chunk) {
                uint8_t buf[8];
                // Write animation control header
                apng->acTL_offset = avio_tell(io_context);
                AV_WB32(buf, UINT_MAX); // number of frames (filled in later)
                AV_WB32(buf + 4, apng->plays);
                apng_write_chunk(io_context, MKBETAG('a', 'c', 'T', 'L'), buf, 8);
            }
        }

        existing_fcTL_chunk = apng_find_chunk(MKBETAG('f', 'c', 'T', 'L'), apng->prev_packet->data, apng->prev_packet->size);
        if (existing_fcTL_chunk) {
            AVRational delay;

            existing_fcTL_chunk += 8;
            delay.num = AV_RB16(existing_fcTL_chunk + 20);
            delay.den = AV_RB16(existing_fcTL_chunk + 22);

            if (delay.num == 0 && delay.den == 0) {
                if (packet) {
                    int64_t delay_num_raw = (packet->dts - apng->prev_packet->dts) * codec_stream->time_base.num;
                    int64_t delay_den_raw = codec_stream->time_base.den;
                    if (!av_reduce(&delay.num, &delay.den, delay_num_raw, delay_den_raw, USHRT_MAX) &&
                        !apng->framerate_warned) {
                        av_log(format_context, AV_LOG_WARNING,
                               "Frame rate is too high or specified too precisely. Unable to copy losslessly.\n");
                        apng->framerate_warned = 1;
                    }
                } else if (apng->last_delay.num > 0) {
                    delay = apng->last_delay;
                } else {
                    delay = apng->prev_delay;
                }

                // Update frame control header with new delay
                AV_WB16(existing_fcTL_chunk + 20, delay.num);
                AV_WB16(existing_fcTL_chunk + 22, delay.den);
                AV_WB32(existing_fcTL_chunk + 26, ~av_crc(av_crc_get_table(AV_CRC_32_IEEE_LE), ~0U, existing_fcTL_chunk - 4, 26 + 4));
            }
            apng->prev_delay = delay;
        }

        // Write frame data
        avio_write(io_context, apng->prev_packet->data, apng->prev_packet->size);
    }
    ++apng->frame_number;

    av_packet_unref(apng->prev_packet);
    if (packet)
        av_copy_packet(apng->prev_packet, packet);
    return 0;
}

static int apng_write_packet(AVFormatContext *format_context, AVPacket *packet)
{
    APNGMuxContext *apng = format_context->priv_data;
    int ret;

    if (!apng->prev_packet) {
        apng->prev_packet = av_malloc(sizeof(*apng->prev_packet));
        if (!apng->prev_packet)
            return AVERROR(ENOMEM);

        av_copy_packet(apng->prev_packet, packet);
    } else {
        ret = flush_packet(format_context, packet);
        if (ret < 0)
            return ret;
    }

    return 0;
}

static int apng_write_trailer(AVFormatContext *format_context)
{
    APNGMuxContext *apng = format_context->priv_data;
    AVIOContext *io_context = format_context->pb;
    uint8_t buf[8];
    int ret;

    if (apng->prev_packet) {
        ret = flush_packet(format_context, NULL);
        av_freep(&apng->prev_packet);
        if (ret < 0)
            return ret;
    }

    apng_write_chunk(io_context, MKBETAG('I', 'E', 'N', 'D'), NULL, 0);

    if (apng->acTL_offset && io_context->seekable) {
        avio_seek(io_context, apng->acTL_offset, SEEK_SET);

        AV_WB32(buf, apng->frame_number);
        AV_WB32(buf + 4, apng->plays);
        apng_write_chunk(io_context, MKBETAG('a', 'c', 'T', 'L'), buf, 8);
    }

    av_freep(&apng->extra_data);
    apng->extra_data = 0;

    return 0;
}

#define OFFSET(x) offsetof(APNGMuxContext, x)
#define ENC AV_OPT_FLAG_ENCODING_PARAM
static const AVOption options[] = {
    { "plays", "Number of times to play the output: 0 - infinite loop, 1 - no loop", OFFSET(plays),
      AV_OPT_TYPE_INT, { .i64 = 1 }, 0, UINT_MAX, ENC },
    { "final_delay", "Force delay after the last frame", OFFSET(last_delay),
      AV_OPT_TYPE_RATIONAL, { .dbl = 0 }, 0, USHRT_MAX, ENC },
    { NULL },
};

static const AVClass apng_muxer_class = {
    .class_name = "APNG muxer",
    .item_name  = av_default_item_name,
    .version    = LIBAVUTIL_VERSION_INT,
    .option     = options,
};

AVOutputFormat ff_apng_muxer = {
    .name           = "apng",
    .long_name      = NULL_IF_CONFIG_SMALL("Animated Portable Network Graphics"),
    .mime_type      = "image/png",
    .extensions     = "apng",
    .priv_data_size = sizeof(APNGMuxContext),
    .audio_codec    = AV_CODEC_ID_NONE,
    .video_codec    = AV_CODEC_ID_APNG,
    .write_header   = apng_write_header,
    .write_packet   = apng_write_packet,
    .write_trailer  = apng_write_trailer,
    .priv_class     = &apng_muxer_class,
    .flags          = AVFMT_VARIABLE_FPS,
};