ffmpeg decoder plugin: refactor the decoding functions

Move some variables shared between multiple functions to a struct so the
functions don't need too many parameters.

Move initializing the decoder into a separate function to improve
readability and reduce cleanup code duplication.

1 files changed, 103 insertions, 103 deletions

diff --git a/src/decoder/FfmpegDecoderPlugin.cxx b/src/decoder/FfmpegDecoderPlugin.cxx
index 3f3e8a43..a3a98a22 100644
--- a/src/decoder/FfmpegDecoderPlugin.cxx
+++ b/src/decoder/FfmpegDecoderPlugin.cxx
@@ -266,16 +266,22 @@ copy_interleave_frame(const AVCodecContext *codec_context,
 }
 #endif
 
+struct ffmpeg_decoder_context {
+	AVStream *st;
+	AVCodecContext *avctx;
+	AVFrame *frame;
+	AVRational time_base;
+	struct audio_format audio_format;
+};
+
 static enum decoder_command
 ffmpeg_send_packet(struct decoder *decoder, struct input_stream *is,
-		   const AVPacket *packet,
-		   AVCodecContext *codec_context,
-		   const AVRational *time_base,
-		   AVFrame *frame)
+		   struct ffmpeg_decoder_context *dec,
+		   const AVPacket *packet)
 {
 	if (packet->pts >= 0 && packet->pts != (int64_t)AV_NOPTS_VALUE)
 		decoder_timestamp(decoder,
-				  time_from_ffmpeg(packet->pts, *time_base));
+				  time_from_ffmpeg(packet->pts, dec->time_base));
 
 	AVPacket packet2 = *packet;
 
@@ -295,12 +301,12 @@ ffmpeg_send_packet(struct decoder *decoder, struct input_stream *is,
 		int audio_size = buffer_size;
 #if LIBAVCODEC_VERSION_INT >= AV_VERSION_INT(53,25,0)
 		int got_frame = 0;
-		int len = avcodec_decode_audio4(codec_context,
-						frame, &got_frame,
+		int len = avcodec_decode_audio4(dec->avctx,
+						dec->frame, &got_frame,
 						&packet2);
 		if (len >= 0 && got_frame) {
-			audio_size = copy_interleave_frame(codec_context,
-							   frame,
+			audio_size = copy_interleave_frame(dec->avctx,
+							   dec->frame,
 							   aligned_buffer,
 							   buffer_size);
 			if (audio_size < 0)
@@ -308,7 +314,7 @@ ffmpeg_send_packet(struct decoder *decoder, struct input_stream *is,
 		} else if (len >= 0)
 			len = -1;
 #else
-		int len = avcodec_decode_audio3(codec_context,
+		int len = avcodec_decode_audio3(dec->avctx,
 						aligned_buffer, &audio_size,
 						&packet2);
 #endif
@@ -327,7 +333,7 @@ ffmpeg_send_packet(struct decoder *decoder, struct input_stream *is,
 
 		cmd = decoder_data(decoder, is,
 				   aligned_buffer, audio_size,
-				   codec_context->bit_rate / 1000);
+				   dec->avctx->bit_rate / 1000);
 	}
 	return cmd;
 }
@@ -403,6 +409,80 @@ ffmpeg_probe(struct decoder *decoder, struct input_stream *is)
 	return format;
 }
 
+static int init_decoder(struct ffmpeg_decoder_context *dec,
+						 AVFormatContext *fmtctx)
+{
+	int audio_stream = ffmpeg_find_audio_stream(fmtctx);
+	if (audio_stream == -1) {
+		g_warning("No audio stream inside\n");
+		return -1;
+	}
+
+	memset(dec, 0, sizeof(dec));
+	dec->st = fmtctx->streams[audio_stream];
+
+	dec->time_base = dec->st->time_base;
+	dec->avctx = dec->st->codec;
+	if (dec->avctx->codec_name[0] != 0)
+		g_debug("codec '%s'", dec->avctx->codec_name);
+
+	AVCodec *codec = avcodec_find_decoder(dec->avctx->codec_id);
+
+	if (!codec) {
+		g_warning("Unsupported audio codec\n");
+		return -1;
+	}
+
+	const enum sample_format sample_format =
+		ffmpeg_sample_format(dec->avctx->sample_fmt);
+	if (sample_format == SAMPLE_FORMAT_UNDEFINED)
+		return -1;
+
+	GError *error = NULL;
+	if (!audio_format_init_checked(&dec->audio_format,
+				       dec->avctx->sample_rate,
+				       sample_format,
+				       dec->avctx->channels, &error)) {
+		g_warning("%s", error->message);
+		g_error_free(error);
+		return -1;
+	}
+
+	dec->frame = avcodec_alloc_frame();
+	if (!dec->frame) {
+		g_warning("Could not allocate frame\n");
+		return -1;
+	}
+
+	/* the audio format must be read from AVCodecContext by now,
+	   because avcodec_open() has been demonstrated to fill bogus
+	   values into AVCodecContext.channels - a change that will be
+	   reverted later by avcodec_decode_audio3() */
+
+#if LIBAVCODEC_VERSION_INT >= AV_VERSION_INT(53,6,0)
+	const int open_result = avcodec_open2(dec->avctx, codec, NULL);
+#else
+	const int open_result = avcodec_open(dec->avctx, codec);
+#endif
+	if (open_result < 0) {
+		g_warning("Could not open codec\n");
+		return -1;
+	}
+
+	return 0;
+}
+
+static void uninit_decoder(struct ffmpeg_decoder_context *dec)
+{
+#if LIBAVCODEC_VERSION_INT >= AV_VERSION_INT(54, 28, 0)
+	avcodec_free_frame(&dec->frame);
+#else
+	av_freep(&dec->frame);
+#endif
+
+	avcodec_close(dec->avctx);
+}
+
 static void
 ffmpeg_decode(struct decoder *decoder, struct input_stream *input)
 {
@@ -447,71 +527,10 @@ ffmpeg_decode(struct decoder *decoder, struct input_stream *input)
 		return;
 	}
 
-	int audio_stream = ffmpeg_find_audio_stream(format_context);
-	if (audio_stream == -1) {
-		g_warning("No audio stream inside\n");
-#if LIBAVFORMAT_VERSION_INT >= AV_VERSION_INT(53,17,0)
-		avformat_close_input(&format_context);
-#else
-		av_close_input_stream(format_context);
-#endif
-		mpd_ffmpeg_stream_close(stream);
-		return;
-	}
-
-	AVStream *av_stream = format_context->streams[audio_stream];
-
-	AVCodecContext *codec_context = av_stream->codec;
-	if (codec_context->codec_name[0] != 0)
-		g_debug("codec '%s'", codec_context->codec_name);
-
-	AVCodec *codec = avcodec_find_decoder(codec_context->codec_id);
-
-	if (!codec) {
-		g_warning("Unsupported audio codec\n");
-#if LIBAVFORMAT_VERSION_INT >= AV_VERSION_INT(53,17,0)
-		avformat_close_input(&format_context);
-#else
-		av_close_input_stream(format_context);
-#endif
-		mpd_ffmpeg_stream_close(stream);
-		return;
-	}
-
-	const enum sample_format sample_format =
-		ffmpeg_sample_format(codec_context->sample_fmt);
-	if (sample_format == SAMPLE_FORMAT_UNDEFINED)
-		return;
-
-	GError *error = NULL;
-	struct audio_format audio_format;
-	if (!audio_format_init_checked(&audio_format,
-				       codec_context->sample_rate,
-				       sample_format,
-				       codec_context->channels, &error)) {
-		g_warning("%s", error->message);
-		g_error_free(error);
-#if LIBAVFORMAT_VERSION_INT >= AV_VERSION_INT(53,17,0)
-		avformat_close_input(&format_context);
-#else
-		av_close_input_stream(format_context);
-#endif
-		mpd_ffmpeg_stream_close(stream);
-		return;
-	}
-
-	/* the audio format must be read from AVCodecContext by now,
-	   because avcodec_open() has been demonstrated to fill bogus
-	   values into AVCodecContext.channels - a change that will be
-	   reverted later by avcodec_decode_audio3() */
-
-#if LIBAVCODEC_VERSION_INT >= AV_VERSION_INT(53,6,0)
-	const int open_result = avcodec_open2(codec_context, codec, NULL);
-#else
-	const int open_result = avcodec_open(codec_context, codec);
-#endif
-	if (open_result < 0) {
-		g_warning("Could not open codec\n");
+	struct ffmpeg_decoder_context dec;
+	int res = init_decoder(&dec, format_context);
+	if (res < 0) {
+		uninit_decoder(&dec);
 #if LIBAVFORMAT_VERSION_INT >= AV_VERSION_INT(53,17,0)
 		avformat_close_input(&format_context);
 #else
@@ -525,21 +544,9 @@ ffmpeg_decode(struct decoder *decoder, struct input_stream *input)
 		? format_context->duration / AV_TIME_BASE
 		: 0;
 
-	decoder_initialized(decoder, &audio_format,
+	decoder_initialized(decoder, &dec.audio_format,
 			    input->seekable, total_time);
 
-	AVFrame *frame = avcodec_alloc_frame();
-	if (!frame) {
-		g_warning("Could not allocate frame\n");
-#if LIBAVFORMAT_VERSION_INT >= AV_VERSION_INT(53,17,0)
-		avformat_close_input(&format_context);
-#else
-		av_close_input_stream(format_context);
-#endif
-		mpd_ffmpeg_stream_close(stream);
-		return;
-	}
-
 	enum decoder_command cmd;
 	do {
 		AVPacket packet;
@@ -547,11 +554,9 @@ ffmpeg_decode(struct decoder *decoder, struct input_stream *input)
 			/* end of file */
 			break;
 
-		if (packet.stream_index == audio_stream)
-			cmd = ffmpeg_send_packet(decoder, input,
-						 &packet, codec_context,
-						 &av_stream->time_base,
-						 frame);
+		if (packet.stream_index == dec.st->index)
+			cmd = ffmpeg_send_packet(decoder, input, &dec,
+						 &packet);
 		else
 			cmd = decoder_get_command(decoder);
 
@@ -560,25 +565,20 @@ ffmpeg_decode(struct decoder *decoder, struct input_stream *input)
 		if (cmd == DECODE_COMMAND_SEEK) {
 			int64_t where =
 				time_to_ffmpeg(decoder_seek_where(decoder),
-					       av_stream->time_base);
+					       dec.st->time_base);
 
-			if (av_seek_frame(format_context, audio_stream, where,
+			if (av_seek_frame(format_context, dec.st->index, where,
 					  AV_TIME_BASE) < 0)
 				decoder_seek_error(decoder);
 			else {
-				avcodec_flush_buffers(codec_context);
+				avcodec_flush_buffers(dec.avctx);
 				decoder_command_finished(decoder);
 			}
 		}
 	} while (cmd != DECODE_COMMAND_STOP);
 
-#if LIBAVCODEC_VERSION_INT >= AV_VERSION_INT(54, 28, 0)
-	avcodec_free_frame(&frame);
-#else
-	av_freep(&frame);
-#endif
+	uninit_decoder(&dec);
 
-	avcodec_close(codec_context);
 #if LIBAVFORMAT_VERSION_INT >= AV_VERSION_INT(53,17,0)
 	avformat_close_input(&format_context);
 #else