[FFmpeg-devel] [PATCH 8/8] apng: Add a basic APNG muxer

Donny Yang work at kota.moe
Sun Mar 29 13:05:45 CEST 2015


Additionally, update some documentation with support for APNG

Signed-off-by: Donny Yang <work at kota.moe>
---
 Changelog                |   1 +
 doc/general.texi         |   2 +
 libavformat/Makefile     |   1 +
 libavformat/allformats.c |   2 +-
 libavformat/apngenc.c    | 250 +++++++++++++++++++++++++++++++++++++++++++++++
 libavformat/version.h    |   4 +-
 6 files changed, 257 insertions(+), 3 deletions(-)
 create mode 100644 libavformat/apngenc.c

diff --git a/Changelog b/Changelog
index dcddca4..3264341 100644
--- a/Changelog
+++ b/Changelog
@@ -12,6 +12,7 @@ version <next>:
 - Detelecine filter
 - Intel QSV-accelerated H.264 encoding
 - MMAL-accelerated H.264 decoding
+- basic APNG encoder and muxer
 
 
 version 2.6:
diff --git a/doc/general.texi b/doc/general.texi
index 85ee219..589b423 100644
--- a/doc/general.texi
+++ b/doc/general.texi
@@ -222,6 +222,7 @@ library:
     @tab Audio format used on the Nintendo Gamecube.
 @item AFC                       @tab   @tab X
     @tab Audio format used on the Nintendo Gamecube.
+ at item APNG                      @tab X @tab X
 @item ASF                       @tab X @tab X
 @item AST                       @tab X @tab X
     @tab Audio format used on the Nintendo Wii.
@@ -508,6 +509,7 @@ following image formats are supported:
 @item Alias PIX    @tab X @tab X
     @tab Alias/Wavefront PIX image format
 @item animated GIF @tab X @tab X
+ at item APNG         @tab X @tab X
 @item BMP          @tab X @tab X
     @tab Microsoft BMP image
 @item BRender PIX  @tab   @tab X
diff --git a/libavformat/Makefile b/libavformat/Makefile
index 2118ff2..5082101 100644
--- a/libavformat/Makefile
+++ b/libavformat/Makefile
@@ -80,6 +80,7 @@ OBJS-$(CONFIG_ANM_DEMUXER)               += anm.o
 OBJS-$(CONFIG_APC_DEMUXER)               += apc.o
 OBJS-$(CONFIG_APE_DEMUXER)               += ape.o apetag.o img2.o
 OBJS-$(CONFIG_APNG_DEMUXER)              += apngdec.o
+OBJS-$(CONFIG_APNG_MUXER)                += apngenc.o
 OBJS-$(CONFIG_AQTITLE_DEMUXER)           += aqtitledec.o subtitles.o
 OBJS-$(CONFIG_ASF_DEMUXER)               += asfdec.o asf.o asfcrypt.o \
                                             avlanguage.o
diff --git a/libavformat/allformats.c b/libavformat/allformats.c
index 26ccc27..ca45db8 100644
--- a/libavformat/allformats.c
+++ b/libavformat/allformats.c
@@ -74,7 +74,7 @@ void av_register_all(void)
     REGISTER_DEMUXER (ANM,              anm);
     REGISTER_DEMUXER (APC,              apc);
     REGISTER_DEMUXER (APE,              ape);
-    REGISTER_DEMUXER (APNG,             apng);
+    REGISTER_MUXDEMUX(APNG,             apng);
     REGISTER_DEMUXER (AQTITLE,          aqtitle);
     REGISTER_MUXDEMUX(ASF,              asf);
     REGISTER_MUXDEMUX(ASS,              ass);
diff --git a/libavformat/apngenc.c b/libavformat/apngenc.c
new file mode 100644
index 0000000..5190453
--- /dev/null
+++ b/libavformat/apngenc.c
@@ -0,0 +1,250 @@
+/*
+ * APNG muxer
+ * Copyright (c) 2015 Donny Yang
+ *
+ * first version by Donny Yang <work at 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 <stdarg.h>
+#include <zlib.h>
+
+#include "avformat.h"
+#include "internal.h"
+#include "libavutil/avassert.h"
+#include "libavutil/intreadwrite.h"
+#include "libavutil/log.h"
+#include "libavutil/opt.h"
+#include "libavcodec/png.h"
+#include "libavcodec/apng.h"
+
+static void apng_write_chunk(AVIOContext *io_context, uint32_t tag,
+                              uint8_t* buf, size_t length)
+{
+    uint32_t crc;
+    uint8_t tagbuf[4];
+
+    avio_wb32(io_context, length);
+    crc = crc32(0, Z_NULL, 0);
+    AV_WB32(tagbuf, tag);
+    crc = crc32(crc, tagbuf, 4);
+    avio_wb32(io_context, tag);
+    if (length > 0) {
+        crc = crc32(crc, buf, length);
+        avio_write(io_context, buf, length);
+    }
+    avio_wb32(io_context, crc);
+}
+
+typedef struct APNGMuxContext {
+    AVClass *class;
+    uint32_t plays;
+    AVRational last_delay;
+
+    uint64_t acTL_offset;
+    uint32_t sequence_number;
+    uint32_t frame_number;
+
+    AVPacket *prev_packet;
+    AVRational prev_delay;
+} APNGMuxContext;
+
+static int apng_write_header(AVFormatContext *format_context)
+{
+    APNGMuxContext *apng = format_context->priv_data;
+    AVStream *codec_stream;
+
+    if (format_context->nb_streams != 1 ||
+        format_context->streams[0]->codec->codec_type != AVMEDIA_TYPE_VIDEO ||
+        format_context->streams[0]->codec->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);
+    }
+    codec_stream = format_context->streams[0];
+
+    if (codec_stream->time_base.num > USHRT_MAX || codec_stream->time_base.den > USHRT_MAX) {
+        av_log(format_context, AV_LOG_WARNING,
+               "Frame rate is too high or specified too precisely. Unable to copy losslessly.\n");
+    }
+
+    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);
+    }
+
+    // Real headers are written when they are copied from the encoder
+
+    return 0;
+}
+
+static void 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];
+    AVCodecContext *codec_context = codec_stream->codec;
+    uint8_t *frame_start;
+    uint8_t buf[26];
+    AVRational delay;
+
+    av_assert0(apng->prev_packet);
+    frame_start = apng->prev_packet->data;
+
+    if (apng->frame_number == 0 && !packet) {
+        av_log(format_context, AV_LOG_WARNING, "Only a single frame so saving as a normal PNG.\n");
+    } else {
+        if (apng->frame_number == 0) {
+            frame_start += 8; // skip PNGSIG
+            while (AV_RB32(frame_start + 4) != MKBETAG('I', 'D', 'A', 'T'))
+                frame_start += AV_RB32(frame_start) + 12;
+
+            // Write normal PNG headers
+            avio_write(io_context, apng->prev_packet->data, frame_start - apng->prev_packet->data);
+
+            // 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);
+        }
+
+        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;
+            av_reduce(&delay.num, &delay.den, delay_num_raw, delay_den_raw, USHRT_MAX);
+        } else if (apng->last_delay.den > 0) {
+            delay = apng->last_delay;
+        } else {
+            delay = apng->prev_delay;
+        }
+        apng->prev_delay = delay;
+
+        AV_WB32(buf, apng->sequence_number);
+        AV_WB32(buf + 4, codec_context->width);
+        AV_WB32(buf + 8, codec_context->height);
+        AV_WB32(buf + 12, 0); // x offset
+        AV_WB32(buf + 16, 0); // y offset
+        AV_WB16(buf + 20, delay.num);
+        AV_WB16(buf + 22, delay.den);
+        buf[24] = APNG_DISPOSE_OP_BACKGROUND;
+        buf[25] = APNG_BLEND_OP_SOURCE;
+        apng_write_chunk(io_context, MKBETAG('f', 'c', 'T', 'L'), buf, 26);
+        ++apng->sequence_number;
+    }
+
+    if (apng->frame_number == 0) {
+        avio_write(io_context, frame_start, apng->prev_packet->data + apng->prev_packet->size - frame_start);
+    } else {
+        // Need to replace IDAT chunks with fdAT chunks
+        do {
+            uint8_t *next_frame_start = frame_start + AV_RB32(frame_start) + 12;
+            size_t frame_size = AV_RB32(frame_start);
+
+            frame_start += 4;
+            frame_size += 4;
+
+            AV_WB32(frame_start, apng->sequence_number);
+            apng_write_chunk(io_context, MKBETAG('f', 'd', 'A', 'T'), frame_start, frame_size);
+            ++apng->sequence_number;
+
+            frame_start = next_frame_start;
+        } while (frame_start < apng->prev_packet->data + apng->prev_packet->size);
+    }
+    ++apng->frame_number;
+
+    av_free_packet(apng->prev_packet);
+    if (packet)
+        av_copy_packet(apng->prev_packet, packet);
+}
+
+static int apng_write_packet(AVFormatContext *format_context, AVPacket *packet)
+{
+    APNGMuxContext *apng = format_context->priv_data;
+
+    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 {
+        flush_packet(format_context, packet);
+    }
+
+    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];
+
+    if (apng->prev_packet) {
+        flush_packet(format_context, NULL);
+        av_freep(&apng->prev_packet);
+    }
+
+    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, format_context->streams[0]->nb_frames);
+        AV_WB32(buf + 4, apng->plays);
+        apng_write_chunk(io_context, MKBETAG('a', 'c', 'T', 'L'), buf, 8);
+    }
+
+    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     = "png",
+    .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,
+};
diff --git a/libavformat/version.h b/libavformat/version.h
index a183d7f..82a57ee 100644
--- a/libavformat/version.h
+++ b/libavformat/version.h
@@ -30,8 +30,8 @@
 #include "libavutil/version.h"
 
 #define LIBAVFORMAT_VERSION_MAJOR 56
-#define LIBAVFORMAT_VERSION_MINOR  26
-#define LIBAVFORMAT_VERSION_MICRO 101
+#define LIBAVFORMAT_VERSION_MINOR  27
+#define LIBAVFORMAT_VERSION_MICRO 100
 
 #define LIBAVFORMAT_VERSION_INT AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \
                                                LIBAVFORMAT_VERSION_MINOR, \
-- 
2.3.4


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