Support MPEG2 decompression.

1 files changed, 143 insertions, 0 deletions

diff --git a/src/mpeg2_transcode.cc b/src/mpeg2_transcode.cc
new file mode 100644
index 00000000..ab77f0e1
--- /dev/null
+++ b/src/mpeg2_transcode.cc
@@ -0,0 +1,143 @@
+/*
+    Copyright (C) 2023 Carl Hetherington <cth@carlh.net>
+
+    This file is part of libdcp.
+
+    libdcp is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    libdcp 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 General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with libdcp.  If not, see <http://www.gnu.org/licenses/>.
+
+    In addition, as a special exception, the copyright holders give
+    permission to link the code of portions of this program with the
+    OpenSSL library under certain conditions as described in each
+    individual source file, and distribute linked combinations
+    including the two.
+
+    You must obey the GNU General Public License in all respects
+    for all of the code used other than OpenSSL.  If you modify
+    file(s) with this exception, you may extend this exception to your
+    version of the file(s), but you are not obligated to do so.  If you
+    do not wish to do so, delete this exception statement from your
+    version.  If you delete this exception statement from all source
+    files in the program, then also delete it here.
+*/
+
+
+#include "compose.hpp"
+#include "exceptions.h"
+#include "mono_mpeg2_picture_frame.h"
+#include "mpeg2_transcode.h"
+extern "C" {
+#include <libavcodec/avcodec.h>
+}
+
+
+using std::shared_ptr;
+using std::vector;
+using namespace dcp;
+
+
+MPEG2Codec::~MPEG2Codec()
+{
+	avcodec_free_context(&_context);
+}
+
+
+
+MPEG2Decompressor::MPEG2Decompressor()
+{
+	_codec = avcodec_find_decoder_by_name("mpeg2video");
+	if (!_codec) {
+		throw MPEG2CodecError("could not find codec");
+	}
+
+	_context = avcodec_alloc_context3(_codec);
+	if (!_context) {
+		throw MPEG2CodecError("could not allocate codec context");
+	}
+
+	int const r = avcodec_open2(_context, _codec, nullptr);
+	if (r < 0) {
+		avcodec_free_context(&_context);
+		throw MPEG2CodecError("could not open codec");
+	}
+
+	_decompressed_frame = av_frame_alloc();
+	if (!_decompressed_frame) {
+		throw std::bad_alloc();
+	}
+}
+
+
+MPEG2Decompressor::~MPEG2Decompressor()
+{
+	av_frame_free(&_decompressed_frame);
+}
+
+
+vector<FFmpegImage>
+MPEG2Decompressor::decompress_frame(shared_ptr<const MonoMPEG2PictureFrame> frame)
+{
+	/* XXX: can we avoid this? */
+	auto copy = av_malloc(frame->size() + AV_INPUT_BUFFER_PADDING_SIZE);
+	if (!copy) {
+		throw std::bad_alloc();
+	}
+	memcpy(copy, frame->data(), frame->size());
+
+	AVPacket packet;
+	av_init_packet(&packet);
+	av_packet_from_data(&packet, reinterpret_cast<uint8_t*>(copy), frame->size());
+
+	auto images = decompress_packet(&packet);
+
+	av_packet_unref(&packet);
+
+	return images;
+}
+
+
+vector<FFmpegImage>
+MPEG2Decompressor::flush()
+{
+	return decompress_packet(nullptr);
+}
+
+
+vector<FFmpegImage>
+MPEG2Decompressor::decompress_packet(AVPacket* packet)
+{
+	int const r = avcodec_send_packet(_context, packet);
+	if (r < 0) {
+		throw MPEG2DecompressionError(String::compose("avcodec_send_packet failed (%1)", r));
+	}
+
+	vector<FFmpegImage> images;
+	while (true) {
+		int const r = avcodec_receive_frame(_context, _decompressed_frame);
+		if (r == AVERROR(EAGAIN) || r == AVERROR_EOF) {
+			break;
+		} else if (r < 0) {
+			throw MPEG2DecompressionError("avcodec_receive_frame failed");
+		}
+
+		auto clone = av_frame_clone(_decompressed_frame);
+		if (!clone) {
+			throw std::bad_alloc();
+		}
+
+		images.push_back(FFmpegImage(clone));
+	}
+
+	return images;
+}
+