From 8d090d20f9a9bf0286d55864f5b7c7fd84b337d7 Mon Sep 17 00:00:00 2001
From: Andreas Unterweger <[email protected]>
Date: Wed, 2 Oct 2013 18:08:51 +0200
Subject: [PATCH] Added an Libav API usage example
---
doc/example/Makefile | 15 ++
doc/example/mp3_aac.c | 692 +++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 707 insertions(+)
create mode 100644 doc/example/Makefile
create mode 100644 doc/example/mp3_aac.c
diff --git a/doc/example/Makefile b/doc/example/Makefile
new file mode 100644
index 0000000..ddc53bb
--- /dev/null
+++ b/doc/example/Makefile
@@ -0,0 +1,15 @@
+CC=gcc
+
+CFLAGS=-c -Wall
+LDFLAGS=-lavformat -lavcodec -lavresample -lavutil -lvo-aacenc -lpthread -lm
+
+all: mp3_to_aac
+
+mp3_to_aac: mp3_aac
+ $(CC) mp3_aac.o -o mp3_to_aac.exe $(LDFLAGS)
+
+mp3_aac: mp3_aac.c
+ $(CC) $(CFLAGS) mp3_aac.c
+
+clean:
+ rm -rf *.o *.exe
diff --git a/doc/example/mp3_aac.c b/doc/example/mp3_aac.c
new file mode 100644
index 0000000..242b95f
--- /dev/null
+++ b/doc/example/mp3_aac.c
@@ -0,0 +1,692 @@
+/*
+ * This file is part of Libav.
+ *
+ * Libav 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.
+ *
+ * Libav 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 Libav; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file MP3 to AAC converter
+ * Convert an MP3 file to an AAC in an MP4 container using Libav.
+ * Requires libvo_aacenc to compile.
+ * Use -lavformat -lavcodec -lavresample -lavutil -lvo-aacenc -lpthread -lm
+ * @author Andreas Unterweger
+ */
+
+#include <stdio.h>
+#include <libavformat/avformat.h>
+#include <libavformat/avio.h>
+#include <libavcodec/avcodec.h>
+#include <libavutil/audio_fifo.h>
+#include <libavutil/opt.h>
+#include <libavresample/avresample.h>
+
+/** The input file path */
+#define INPUT_FILENAME "test.mp3"
+/** The output file path */
+#define OUTPUT_FILENAME "test.mp4"
+/** The output codec name (AAC via libvo_aacenc) */
+#define OUTPUT_CODEC_NAME "libvo_aacenc"
+/** The output bit rate in kbit/s */
+#define OUTPUT_BIT_RATE 48000
+/** The number of output channels */
+#define OUTPUT_CHANNELS 2
+/** The audio sample output format */
+#define OUTPUT_SAMPLE_FORMAT AV_SAMPLE_FMT_S16
+
+/**
+ * Convert an error code into a text message.
+ * @param error Error code to be converted
+ * @return Corresponding error text (not thread-safe)
+ */
+static char *const get_error_text(const int error)
+{
+ static char error_buffer[255];
+ av_strerror(error, error_buffer, sizeof(error_buffer));
+ return error_buffer;
+}
+
+/** Open an input file and the required decoder. */
+static int open_input_file(const char *filename,
+ AVFormatContext **input_format_context,
+ AVCodecContext **input_codec_context)
+{
+ AVCodec *input_codec;
+ int error;
+ /** Open the input file to read from it. */
+ if ((error = avformat_open_input(input_format_context, filename, NULL, NULL))
< 0) {
+ fprintf(stderr, "Could not open input file '%s' (error '%s')\n",
+ filename, get_error_text(error));
+ return error;
+ }
+ /** Get information on the input file (number of streams etc.). */
+ if ((error = avformat_find_stream_info(*input_format_context, NULL)) < 0) {
+ fprintf(stderr, "Could not open find stream info (error '%s')\n",
+ get_error_text(error));
+ return error;
+ }
+ /** Make sure that there is only one stream in the input file. */
+ if ((*input_format_context)->nb_streams != 1) {
+ fprintf(stderr, "Expected one audio input stream, but found %d\n",
+ (*input_format_context)->nb_streams);
+ avformat_close_input(input_format_context);
+ return AVERROR_EXIT;
+ }
+ /** Find a decoder for the audio stream. */
+ if (!(input_codec =
avcodec_find_decoder((*input_format_context)->streams[0]->codec->codec_id))) {
+ fprintf(stderr, "Could not find input codec\n");
+ avformat_close_input(input_format_context);
+ return AVERROR_EXIT;
+ }
+ /** Open the decoder for the audio stream to use it later. */
+ if ((error = avcodec_open2((*input_format_context)->streams[0]->codec,
input_codec, NULL)) < 0) {
+ fprintf(stderr, "Could not open input codec (error '%s')\n",
get_error_text(error));
+ avformat_close_input(input_format_context);
+ return error;
+ }
+ /** Save the decoder context for easier access later. */
+ *input_codec_context = (*input_format_context)->streams[0]->codec;
+ return 0;
+}
+
+/**
+ * Open an output file and the required encoder.
+ * Also set some basic encoder parameters.
+ * Some of these parameters are based on the input file's parameters.
+ */
+static int open_output_file(const char *filename,
+ AVCodecContext *input_codec_context,
+ AVFormatContext **output_format_context,
+ AVCodecContext **output_codec_context)
+{
+ AVIOContext *output_io_context = NULL;
+ AVStream *stream = NULL;
+ AVCodec *output_codec = NULL;
+ int error;
+ /** Open the output file to write to it. */
+ if ((error = avio_open(&output_io_context, filename, AVIO_FLAG_WRITE)) <
0) {
+ fprintf(stderr, "Could not open output file '%s' (error '%s')\n",
+ filename, get_error_text(error));
+ return error;
+ }
+ /** Create a new format context for the output container format. */
+ if (!(*output_format_context = avformat_alloc_context())) {
+ fprintf(stderr, "Could not allocate output format context\n");
+ return AVERROR(ENOMEM);
+ }
+ /** Associate the output file (pointer) with the container format context.
*/
+ (*output_format_context)->pb = output_io_context;
+ /** Guess the desired container format based on the file extension. */
+ if (!((*output_format_context)->oformat = av_guess_format(NULL, filename,
NULL))) {
+ fprintf(stderr, "Could not find output file format\n");
+ avformat_close_input(output_format_context);
+ return AVERROR_EXIT;
+ }
+ /** Find the encoder to be used by its name. */
+ if (!(output_codec = avcodec_find_encoder_by_name(OUTPUT_CODEC_NAME))) {
+ fprintf(stderr, "Could not find output codec '%s'\n",
OUTPUT_CODEC_NAME);
+ avformat_close_input(output_format_context);
+ return AVERROR_EXIT;
+ }
+ /** Create a new audio stream in the output file container. */
+ if (!(stream = avformat_new_stream(*output_format_context, output_codec)))
{
+ fprintf(stderr, "Could not create new stream\n");
+ avformat_close_input(output_format_context);
+ return AVERROR(ENOMEM);
+ }
+ /** Save the encoder context for easiert access later. */
+ *output_codec_context = stream->codec;
+ /**
+ * Set the basic encoder parameters.
+ * The input file's sample rate is used to avoid a sample rate conversion.
+ */
+ (*output_codec_context)->channels = OUTPUT_CHANNELS;
+ (*output_codec_context)->sample_rate = input_codec_context->sample_rate;
+ (*output_codec_context)->sample_fmt = AV_SAMPLE_FMT_S16;
+ (*output_codec_context)->bit_rate = OUTPUT_BIT_RATE;
+ /**
+ * Some container formats (like MP4) require global headers to be present
+ * Mark the encoder so that it behaves accordingly.
+ */
+ if ((*output_format_context)->oformat->flags & AVFMT_GLOBALHEADER)
+ (*output_codec_context)->flags |= CODEC_FLAG_GLOBAL_HEADER;
+ /** Open the encoder for the audio stream to use it later. */
+ if ((error = avcodec_open2(*output_codec_context, output_codec, NULL)) <
0) {
+ fprintf(stderr, "Could not open output codec (error '%s')\n",
get_error_text(error));
+ avformat_close_input(output_format_context);
+ return error;
+ }
+ return 0;
+}
+
+/** Initialize one data packet for reading or writing. */
+static void init_packet(AVPacket *packet)
+{
+ av_init_packet(packet);
+ /** Set the packet data and size so that it is recognized as being empty.
*/
+ packet->data = NULL;
+ packet->size = 0;
+}
+
+/** Initialize one audio frame for reading from the input file */
+static int init_input_frame(AVFrame **frame)
+{
+ if (!(*frame = avcodec_alloc_frame())) {
+ fprintf(stderr, "Could not allocate input frame\n");
+ return AVERROR(ENOMEM);
+ }
+ avcodec_get_frame_defaults(*frame);
+ return 0;
+}
+
+/**
+ * Initialize the audio resampler based on the input and output codec settings.
+ * If the input and output sample formats differ, a conversion is required
+ * libavresample takes care of this, but requires initialization.
+ */
+static int init_resampler(AVCodecContext *input_codec_context,
+ AVCodecContext *output_codec_context,
+ AVAudioResampleContext **resample_context)
+{
+ /**
+ * Only initialize the resampler if it is necessary, i.e.,
+ * if and only if the sample formats differ.
+ */
+ if (input_codec_context->sample_fmt != output_codec_context->sample_fmt ||
+ input_codec_context->channels != output_codec_context->channels) {
+ int error;
+ /** Create a resampler context for the conversion. */
+ if (!(*resample_context = avresample_alloc_context())) {
+ fprintf(stderr, "Could not allocate resample context\n");
+ return AVERROR(ENOMEM);
+ }
+ /**
+ * Set the conversion parameters.
+ * Default channel layouts based on the number of channels
+ * are assumed for simplicity (they are sometimes not detected
+ * properly by the demuxer and/or decoder).
+ */
+ av_opt_set_int(*resample_context, "in_channel_layout",
+ av_get_default_channel_layout(input_codec_context->channels), 0);
+ av_opt_set_int(*resample_context, "out_channel_layout",
+ av_get_default_channel_layout(output_codec_context->channels), 0);
+ av_opt_set_int(*resample_context, "in_sample_rate",
+ input_codec_context->sample_rate, 0);
+ av_opt_set_int(*resample_context, "out_sample_rate",
+ output_codec_context->sample_rate, 0);
+ av_opt_set_int(*resample_context, "in_sample_fmt",
+ input_codec_context->sample_fmt, 0);
+ av_opt_set_int(*resample_context, "out_sample_fmt",
+ output_codec_context->sample_fmt, 0);
+ /** Open the resampler with the specified parameters. */
+ if ((error = avresample_open(*resample_context)) < 0) {
+ fprintf(stderr, "Could not open resample context\n");
+ avresample_free(resample_context);
+ return error;
+ }
+ }
+ return 0;
+}
+
+/** Initialize a FIFO buffer for the audio samples to be encoded. */
+static int init_fifo(AVAudioFifo **fifo)
+{
+ /** Create the FIFO buffer based on the specified output sample format. */
+ if (!(*fifo = av_audio_fifo_alloc(OUTPUT_SAMPLE_FORMAT, OUTPUT_CHANNELS,
1))) {
+ fprintf(stderr, "Could not allocate FIFO\n");
+ return AVERROR(ENOMEM);
+ }
+ return 0;
+}
+
+/** Write the header of the output file container. */
+static int write_output_file_header(AVFormatContext *output_format_context)
+{
+ int error;
+ if ((error = avformat_write_header(output_format_context, NULL)) < 0) {
+ fprintf(stderr, "Could not write output file header (error '%s')\n",
get_error_text(error));
+ return error;
+ }
+ return 0;
+}
+
+/** Deallocate one packet. */
+static void uninit_packet(AVPacket *packet)
+{
+ av_free_packet(packet);
+}
+
+/** Decode one audio frame from the input file. */
+static int decode_audio_frame(AVFrame *frame,
+ AVFormatContext *input_format_context,
+ AVCodecContext *input_codec_context,
+ int *data_present)
+{
+ /** Packet used for temporary storage. */
+ AVPacket input_packet;
+ int error;
+ init_packet(&input_packet);
+ /** Read one audio frame from the input file into a temporary packet. */
+ if ((error = av_read_frame(input_format_context, &input_packet)) < 0) {
+ /** Abort on end of file, but do not treat it as an actual error. */
+ if (error == AVERROR_EOF) {
+ *data_present = 0;
+ uninit_packet(&input_packet);
+ return 0;
+ }
+ fprintf(stderr, "Could not read frame (error '%s')\n",
get_error_text(error));
+ return error;
+ }
+ /**
+ * Decode the audio frame stored in the temporary packet.
+ * The input audio stream decoder is used to do this.
+ */
+ if ((error = avcodec_decode_audio4(input_codec_context, frame, data_present,
&input_packet)) < 0) {
+ fprintf(stderr, "Could not decode frame (error '%s')\n",
get_error_text(error));
+ uninit_packet(&input_packet);
+ return error;
+ }
+ uninit_packet(&input_packet);
+ return 0;
+}
+
+/**
+ * Initialize a temporary storage for the specified number of audio samples.
+ * The conversion requires temporary storage due to the different format.
+ * The number of audio samples to be allocated is specified in frame_size.
+ */
+static int init_converted_samples(uint8_t ***converted_input_samples,
+ AVCodecContext *output_codec_context,
+ int frame_size)
+{
+ int error;
+ /**
+ * Allocate as many pointers as there are audio channels.
+ * Each pointer will later point to the audio samples of the corresponding
+ * channels (although it may be NULL for interleaved formats).
+ */
+ if (!(*converted_input_samples = calloc(output_codec_context->channels,
sizeof(**converted_input_samples)))) {
+ fprintf(stderr, "Could not allocate converted input sample
pointers\n");
+ return AVERROR(ENOMEM);
+ }
+ /**
+ * Allocate memory for the samples of all channels in one consecutive
+ * block for convenience.
+ */
+ if ((error = av_samples_alloc(*converted_input_samples, NULL,
output_codec_context->channels,
+ frame_size, output_codec_context->sample_fmt,
0)) < 0) {
+ fprintf(stderr, "Could not allocate converted input samples (error
'%s')\n", get_error_text(error));
+ av_freep(&converted_input_samples[0]);
+ free(converted_input_samples);
+ return error;
+ }
+ return 0;
+}
+
+/**
+ * Convert the input audio samples into the output sample format.
+ * The conversion happens on a per-frame basis, the size of which is specified
+ * by frame_size.
+ */
+static int convert_samples(uint8_t **input_data,
+ uint8_t **converted_data, const int frame_size,
+ AVAudioResampleContext *resample_context)
+{
+ int error;
+ /** Convert the samples using the resampler. */
+ if ((error = avresample_convert(resample_context, converted_data, 0,
+ frame_size, input_data, 0, frame_size)) <
0) {
+ fprintf(stderr, "Could not convert input samples (error '%s')\n",
+ get_error_text(error));
+ return error;
+ }
+ /**
+ * Perform a sanity check so that the number of converted samples is
+ * not greater than the number of samples to be converted.
+ * If the sample rates differ, this case has to be handled differently
+ */
+ if (avresample_available(resample_context)) {
+ fprintf(stderr, "Converted samples left over\n");
+ return AVERROR_EXIT;
+ }
+ return 0;
+}
+
+/** Add converted input audio samples to the FIFO buffer for later processing.
*/
+static int add_samples_to_fifo(AVAudioFifo *fifo,
+ uint8_t **converted_input_samples,
+ const int frame_size)
+{
+ int error;
+ /**
+ * Make the FIFO as large as it needs to be to hold both,
+ * the old and the new samples.
+ */
+ if ((error = av_audio_fifo_realloc(fifo, av_audio_fifo_size(fifo) +
frame_size)) < 0) {
+ fprintf(stderr, "Could not reallocate FIFO\n");
+ return error;
+ }
+ /** Store the new samples in the FIFO buffer. */
+ if (av_audio_fifo_write(fifo, (void **)converted_input_samples, frame_size)
< frame_size) {
+ fprintf(stderr, "Could not write data to FIFO\n");
+ return AVERROR_EXIT;
+ }
+ return 0;
+}
+
+/** Deallocate one frame used for reading from the input file. */
+static void uninit_input_frame(AVFrame *frame)
+{
+ avcodec_free_frame(&frame);
+}
+
+/**
+ * Read one audio frame from the input file, decodes, converts and stores
+ * it in the FIFO buffer.
+ */
+static int read_decode_convert_and_store(AVAudioFifo *fifo, AVFormatContext
*input_format_context,
+ AVCodecContext *input_codec_context,
+ AVCodecContext *output_codec_context,
+ AVAudioResampleContext
*resampler_context, int *finished)
+{
+ /** Temporary storage of the input samples of the frame read from the
file. */
+ AVFrame *input_frame = NULL;
+ /** Temporary storage for the converted input samples. */
+ uint8_t **converted_input_samples = NULL;
+ int input_frame_size;
+ int data_present;
+ int ret = AVERROR_EXIT;
+
+ /** Initialize temporary storage for one input frame. */
+ if (init_input_frame(&input_frame))
+ goto cleanup;
+ /** Decode one frame worth of audio samples. */
+ if (decode_audio_frame(input_frame, input_format_context, input_codec_context,
&data_present))
+ goto cleanup;
+ /**
+ * If there is no more data, we are at the end of the file.
+ * Although this may have other reasons as well, an error
+ * would have printed an error message above and this code
+ * path could not have been reached.
+ */
+ if (!data_present) {
+ *finished = 1;
+ ret = 0;
+ goto cleanup;
+ }
+ input_frame_size = input_codec_context->frame_size;
+ /** Initialize the temporary storage for the converted input samples. */
+ if (init_converted_samples(&converted_input_samples, output_codec_context,
input_frame_size))
+ goto cleanup;
+ /**
+ * Convert the input samples to the desired output sample format.
+ * This requires a temporary storage provided by converted_input_samples.
+ */
+ if (convert_samples(input_frame->data, converted_input_samples,
input_frame_size, resampler_context))
+ goto cleanup;
+ /** Add the converted input samples to the FIFO buffer for later
processing. */
+ if (add_samples_to_fifo(fifo, converted_input_samples, input_frame_size))
+ goto cleanup;
+ ret = 0;
+
+cleanup:
+ if (converted_input_samples) {
+ av_freep(&converted_input_samples[0]);
+ free(converted_input_samples);
+ }
+ if (input_frame)
+ uninit_input_frame(input_frame);
+ return ret;
+}
+
+/** Deallocate one frame used for writing to the output file. */
+static void uninit_output_frame(AVFrame *frame)
+{
+ /**
+ * Make sure that the frame's data is freed.
+ * Otherwise, there will be memory leaks.
+ */
+ if (frame->data)
+ av_freep(frame->data);
+ avcodec_free_frame(&frame);
+}
+
+/**
+ * Initialize one input frame for writing to the output file.
+ * The frame will be exactly frame_size samples large.
+ */
+static int init_output_frame(AVFrame **frame,
+ AVCodecContext *output_codec_context,
+ int frame_size)
+{
+ uint8_t *samples;
+ int buffer_size;
+ int error;
+ /** Create a new frame to store the audio samples. */
+ if (!(*frame = avcodec_alloc_frame())) {
+ fprintf(stderr, "Could not allocate output frame\n");
+ return AVERROR_EXIT;
+ }
+ /** Set the frame's parameters, especially its size and format. */
+ avcodec_get_frame_defaults(*frame);
+ (*frame)->nb_samples = frame_size;
+ (*frame)->format = output_codec_context->sample_fmt;
+ /**
+ * Determine the amount of memory required to store the desired number
+ * of audio samples.
+ */
+ buffer_size = av_samples_get_buffer_size(NULL,
output_codec_context->channels,
+ frame_size,
output_codec_context->sample_fmt, 0);
+ /** Allocate the memory required to store the audio samples. */
+ if (!(samples = av_malloc(buffer_size))) {
+ fprintf(stderr, "Could not allocate output samples\n");
+ uninit_output_frame(*frame);
+ return AVERROR(ENOMEM);
+ }
+ /**
+ * Make the allocated memory for samples available to the created frame.
+ * This call will make sure that the audio frame can hold as many
+ * samples as specified using the allocated memory from above.
+ */
+ if ((error = avcodec_fill_audio_frame(*frame,
output_codec_context->channels,
+ output_codec_context->sample_fmt,
samples,
+ buffer_size, 0)) < 0) {
+ fprintf(stderr, "Could not fill output frame (error '%s')\n",
get_error_text(error));
+ uninit_output_frame(*frame);
+ return error;
+ }
+ return 0;
+}
+
+/** Encode one frame worth of audio to the output file. */
+static int encode_audio_frame(AVFrame *frame, AVFormatContext
*output_format_context,
+ AVCodecContext *output_codec_context, int
*data_present)
+{
+ /** Packet used for temporary storage. */
+ AVPacket output_packet;
+ int error;
+ init_packet(&output_packet);
+ /**
+ * Encode the audio frame and store it in the temporary packet.
+ * The output audio stream encoder is used to do this.
+ */
+ if ((error = avcodec_encode_audio2(output_codec_context, &output_packet,
frame, data_present)) < 0) {
+ fprintf(stderr, "Could not encode frame (error '%s')\n",
get_error_text(error));
+ uninit_packet(&output_packet);
+ return error;
+ }
+ /** Write one audio frame from the temporary packet to the output file. */
+ if ((error = av_write_frame(output_format_context, &output_packet)) < 0) {
+ fprintf(stderr, "Could not write frame (error '%s')\n",
get_error_text(error));
+ uninit_packet(&output_packet);
+ return error;
+ }
+ uninit_packet(&output_packet);
+ return 0;
+}
+
+/**
+ * Load one audio frame from the FIFO buffer, encode and write it to the
+ * output file.
+ */
+static int load_encode_and_write(AVAudioFifo *fifo, AVFormatContext
*output_format_context,
+ AVCodecContext *output_codec_context)
+{
+ /** Temporary storage of the output samples of the frame written to the
file. */
+ AVFrame *output_frame;
+ /**
+ * Use the maximum number of possible samples per frame.
+ * If there is less than the maximum possible frame size in the FIFO
+ * buffer use this number. Otherwise, use the maximum possible frame size
+ */
+ const int frame_size = (av_audio_fifo_size(fifo) <
output_codec_context->frame_size ? av_audio_fifo_size(fifo) :
output_codec_context->frame_size);
+ int data_written;
+ /** Initialize temporary storage for one output frame. */
+ if (init_output_frame(&output_frame, output_codec_context, frame_size)) {
+ return AVERROR_EXIT;
+ }
+ /**
+ * Read as many samples from the FIFO buffer as required to fill the frame.
+ * The samples are stored in the frame temporarily.
+ */
+ if (av_audio_fifo_read(fifo, (void **)output_frame->data, frame_size) <
frame_size) {
+ fprintf(stderr, "Could not read data from FIFO\n");
+ uninit_output_frame(output_frame);
+ return AVERROR_EXIT;
+ }
+ /** Encode one frame worth of audio samples. */
+ if (encode_audio_frame(output_frame, output_format_context,
output_codec_context, &data_written)) {
+ uninit_output_frame(output_frame);
+ return AVERROR_EXIT;
+ }
+ /** If no data has been written, something went wrong and we exit. */
+ if (!data_written) {
+ printf("Warning: No output data written\n");
+ avcodec_free_frame(&output_frame);
+ return AVERROR_EXIT;
+ }
+ uninit_output_frame(output_frame);
+ return 0;
+}
+
+/** Write the trailer of the output file container. */
+static int write_output_file_trailer(AVFormatContext *output_format_context)
+{
+ int error;
+ if ((error = av_write_trailer(output_format_context)) < 0) {
+ fprintf(stderr, "Could not write output file trailer (error '%s')\n",
get_error_text(error));
+ return error;
+ }
+ return 0;
+}
+
+/** Convert an MP3 to an AAC file in an MP4 container. */
+int main(void)
+{
+ AVFormatContext *input_format_context = NULL, *output_format_context =
NULL;
+ AVCodecContext *input_codec_context = NULL, *output_codec_context =
NULL;
+ AVAudioResampleContext *resample_context = NULL;
+ AVAudioFifo *fifo = NULL;
+ int ret = AVERROR_EXIT;
+
+ /** Register all codecs and formats so that they can be used. */
+ av_register_all();
+ /** Open the input file for reading. */
+ if (open_input_file(INPUT_FILENAME, &input_format_context,
&input_codec_context))
+ goto cleanup;
+ /** Open the output file for writing. */
+ if (open_output_file(OUTPUT_FILENAME, input_codec_context,
&output_format_context, &output_codec_context))
+ goto cleanup;
+ /** Initialize the resampler to be able to convert audio sample formats. */
+ if (init_resampler(input_codec_context, output_codec_context,
&resample_context))
+ goto cleanup;
+ /** Initialize the FIFO buffer to store audio samples to be encoded. */
+ if (init_fifo(&fifo))
+ goto cleanup;
+ /** Write the header of the output file container. */
+ if (write_output_file_header(output_format_context))
+ goto cleanup;
+
+ /**
+ * Loop as long as we have input samples to read or output samples
+ * to write; abort as soon as we have neither.
+ */
+ while (1) {
+ /** Use the encoder's desired frame size for processing. */
+ const int output_frame_size = output_codec_context->frame_size;
+ int finished = 0;
+
+ /**
+ * Make sure that there is one frame worth of samples in the FIFO
+ * buffer so that the encoder can do its work.
+ * Since the decoder's and the encoder's frame size may differ, we
+ * need to FIFO buffer to store as many frames worth of input samples
+ * that they make up at least one frame worth of output samples.
+ */
+ while (av_audio_fifo_size(fifo) < output_frame_size) {
+ /**
+ * Decode one frame worth of audio samples, convert it to the
+ * output sample format and put it into the FIFO buffer.
+ */
+ if (read_decode_convert_and_store(fifo, input_format_context,
input_codec_context, output_codec_context, resample_context, &finished))
+ goto cleanup;
+ /**
+ * If we are at the end of the input file, we continue
+ * encoding the remaining audio samples to the output file.
+ */
+ if (finished)
+ break;
+ }
+ /**
+ * If we have enough samples for the encoder, we encode them.
+ * At the end of the file, we pass the remaining samples to
+ * the encoder.
+ */
+ while (av_audio_fifo_size(fifo) >= output_frame_size || (finished &&
av_audio_fifo_size(fifo) > 0))
+ /**
+ * Take one frame worth of audio samples from the FIFO buffer,
+ * encode it and write it to the output file.
+ */
+ if (load_encode_and_write(fifo, output_format_context,
output_codec_context))
+ goto cleanup;
+ /**
+ * If we are at the end of the input file and have encoded
+ * all remaining samples, we can exit this loop and finish.
+ */
+ if (finished)
+ break;
+ }
+
+ /** Write the trailer of the output file container. */
+ if (write_output_file_trailer(output_format_context))
+ goto cleanup;
+ ret = 0;
+
+cleanup:
+ if (fifo)
+ av_audio_fifo_free(fifo);
+ if (resample_context) {
+ avresample_close(resample_context);
+ avresample_free(&resample_context);
+ }
+ if (output_codec_context)
+ avcodec_close(output_codec_context);
+ if (output_format_context)
+ avformat_close_input(&output_format_context);
+ if (input_codec_context)
+ avcodec_close(input_codec_context);
+ if (input_format_context)
+ avformat_close_input(&input_format_context);
+ return ret;
+}
--
1.7.9.5
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