Simple audio converter. More...

#include <stdio.h>
#include "libavformat/avformat.h"
#include "libavformat/avio.h"
#include "libavcodec/avcodec.h"
#include "libavutil/audio_fifo.h"
#include "libavutil/avassert.h"
#include "libavutil/avstring.h"
#include "libavutil/channel_layout.h"
#include "libavutil/frame.h"
#include "libavutil/opt.h"
#include "libswresample/swresample.h"

Macros
#define	OUTPUT_BIT_RATE 96000

#define	OUTPUT_CHANNELS 2

Functions
static int	open_input_file (const char filename, AVFormatContext input_format_context, AVCodecContext *input_codec_context)
	Open an input file and the required decoder. More...

static int	open_output_file (const char filename, AVCodecContext input_codec_context, AVFormatContext output_format_context, AVCodecContext output_codec_context)
	Open an output file and the required encoder. More...

static int	init_packet (AVPacket **packet)
	Initialize one data packet for reading or writing. More...

static int	init_input_frame (AVFrame **frame)
	Initialize one audio frame for reading from the input file. More...

static int	init_resampler (AVCodecContext input_codec_context, AVCodecContext output_codec_context, SwrContext **resample_context)
	Initialize the audio resampler based on the input and output codec settings. More...

static int	init_fifo (AVAudioFifo *fifo, AVCodecContext output_codec_context)
	Initialize a FIFO buffer for the audio samples to be encoded. More...

static int	write_output_file_header (AVFormatContext *output_format_context)
	Write the header of the output file container. More...

static int	decode_audio_frame (AVFrame frame, AVFormatContext input_format_context, AVCodecContext input_codec_context, int data_present, int *finished)
	Decode one audio frame from the input file. More...

static int	init_converted_samples (uint8_t **converted_input_samples, AVCodecContext output_codec_context, int frame_size)
	Initialize a temporary storage for the specified number of audio samples. More...

static int	convert_samples (const uint8_t input_data, uint8_t converted_data, const int frame_size, SwrContext *resample_context)
	Convert the input audio samples into the output sample format. More...

static int	add_samples_to_fifo (AVAudioFifo fifo, uint8_t *converted_input_samples, const int frame_size)
	Add converted input audio samples to the FIFO buffer for later processing. More...

static int	read_decode_convert_and_store (AVAudioFifo fifo, AVFormatContext input_format_context, AVCodecContext input_codec_context, AVCodecContext output_codec_context, SwrContext resampler_context, int finished)
	Read one audio frame from the input file, decode, convert and store it in the FIFO buffer. More...

static int	init_output_frame (AVFrame *frame, AVCodecContext output_codec_context, int frame_size)
	Initialize one input frame for writing to the output file. More...

static int	encode_audio_frame (AVFrame frame, AVFormatContext output_format_context, AVCodecContext output_codec_context, int data_present)
	Encode one frame worth of audio to the output file. More...

static int	load_encode_and_write (AVAudioFifo fifo, AVFormatContext output_format_context, AVCodecContext *output_codec_context)
	Load one audio frame from the FIFO buffer, encode and write it to the output file. More...

static int	write_output_file_trailer (AVFormatContext *output_format_context)
	Write the trailer of the output file container. More...

int	main (int argc, char **argv)

Variables
static int64_t	pts = 0

Detailed Description

Simple audio converter.

Definition in file transcode_aac.c.

Macro Definition Documentation

◆ OUTPUT_BIT_RATE

#define OUTPUT_BIT_RATE 96000

Examples: transcode_aac.c.

Definition at line 48 of file transcode_aac.c.

◆ OUTPUT_CHANNELS

#define OUTPUT_CHANNELS 2

Examples: transcode_aac.c.

Definition at line 50 of file transcode_aac.c.

Function Documentation

◆ open_input_file()

static int open_input_file	(	const char *	filename,
		AVFormatContext **	input_format_context,
		AVCodecContext **	input_codec_context
	)

static

Open an input file and the required decoder.

Parameters

	filename	File to be opened
[out]	input_format_context	Format context of opened file
[out]	input_codec_context	Codec context of opened file

Returns: Error code (0 if successful)

Examples: transcode_aac.c.

Definition at line 59 of file transcode_aac.c.

Referenced by main().

◆ open_output_file()

static int open_output_file	(	const char *	filename,
		AVCodecContext *	input_codec_context,
		AVFormatContext **	output_format_context,
		AVCodecContext **	output_codec_context
	)

static

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.

Parameters

	filename	File to be opened
	input_codec_context	Codec context of input file
[out]	output_format_context	Format context of output file
[out]	output_codec_context	Codec context of output file

Returns: Error code (0 if successful)

Examples: transcode_aac.c.

Definition at line 146 of file transcode_aac.c.

Referenced by main().

◆ init_packet()

static int init_packet ( AVPacket ** packet )

static

Initialize one data packet for reading or writing.

Parameters

[out] packet Packet to be initialized

Returns: Error code (0 if successful)

Examples: transcode_aac.c.

Definition at line 254 of file transcode_aac.c.

Referenced by decode_audio_frame(), and encode_audio_frame().

◆ init_input_frame()

static int init_input_frame ( AVFrame ** frame )

static

Initialize one audio frame for reading from the input file.

Parameters

[out] frame Frame to be initialized

Returns: Error code (0 if successful)

Examples: transcode_aac.c.

Definition at line 268 of file transcode_aac.c.

Referenced by read_decode_convert_and_store().

◆ init_resampler()

static int init_resampler	(	AVCodecContext *	input_codec_context,
		AVCodecContext *	output_codec_context,
		SwrContext **	resample_context
	)

static

Initialize the audio resampler based on the input and output codec settings.

If the input and output sample formats differ, a conversion is required libswresample takes care of this, but requires initialization.

Parameters

	input_codec_context	Codec context of the input file
	output_codec_context	Codec context of the output file
[out]	resample_context	Resample context for the required conversion

Returns: Error code (0 if successful)

Examples: transcode_aac.c.

Definition at line 286 of file transcode_aac.c.

Referenced by main().

◆ init_fifo()

static int init_fifo	(	AVAudioFifo **	fifo,
		AVCodecContext *	output_codec_context
	)

static

Initialize a FIFO buffer for the audio samples to be encoded.

Parameters

[out]	fifo	Sample buffer
	output_codec_context	Codec context of the output file

Returns: Error code (0 if successful)

Examples: transcode_aac.c.

Definition at line 330 of file transcode_aac.c.

Referenced by main().

◆ write_output_file_header()

static int write_output_file_header ( AVFormatContext * output_format_context )

static

Write the header of the output file container.

Parameters

output_format_context Format context of the output file

Returns: Error code (0 if successful)

Examples: transcode_aac.c.

Definition at line 346 of file transcode_aac.c.

Referenced by main().

◆ decode_audio_frame()

static int decode_audio_frame	(	AVFrame *	frame,
		AVFormatContext *	input_format_context,
		AVCodecContext *	input_codec_context,
		int *	data_present,
		int *	finished
	)

static

Decode one audio frame from the input file.

Parameters

	frame	Audio frame to be decoded
	input_format_context	Format context of the input file
	input_codec_context	Codec context of the input file
[out]	data_present	Indicates whether data has been decoded
[out]	finished	Indicates whether the end of file has been reached and all data has been decoded. If this flag is false, there is more data to be decoded, i.e., this function has to be called again.

Returns: Error code (0 if successful)

Examples: transcode_aac.c.

Definition at line 370 of file transcode_aac.c.

Referenced by read_decode_convert_and_store().

◆ init_converted_samples()

static int init_converted_samples	(	uint8_t ***	converted_input_samples,
		AVCodecContext *	output_codec_context,
		int	frame_size
	)

static

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.

Parameters

[out]	converted_input_samples	Array of converted samples. The dimensions are reference, channel (for multi-channel audio), sample.
	output_codec_context	Codec context of the output file
	frame_size	Number of samples to be converted in each round

Returns: Error code (0 if successful)

Examples: transcode_aac.c.

Definition at line 444 of file transcode_aac.c.

Referenced by read_decode_convert_and_store().

◆ convert_samples()

static int convert_samples	(	const uint8_t **	input_data,
		uint8_t **	converted_data,
		const int	frame_size,
		SwrContext *	resample_context
	)

static

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.

Parameters

	input_data	Samples to be decoded. The dimensions are channel (for multi-channel audio), sample.
[out]	converted_data	Converted samples. The dimensions are channel (for multi-channel audio), sample.
	frame_size	Number of samples to be converted
	resample_context	Resample context for the conversion

Returns: Error code (0 if successful)

Examples: transcode_aac.c.

Definition at line 488 of file transcode_aac.c.

Referenced by read_decode_convert_and_store().

◆ add_samples_to_fifo()

static int add_samples_to_fifo	(	AVAudioFifo *	fifo,
		uint8_t **	converted_input_samples,
		const int	frame_size
	)

static

Add converted input audio samples to the FIFO buffer for later processing.

Parameters

fifo	Buffer to add the samples to
converted_input_samples	Samples to be added. The dimensions are channel (for multi-channel audio), sample.
frame_size	Number of samples to be converted

Returns: Error code (0 if successful)

Examples: transcode_aac.c.

Definition at line 514 of file transcode_aac.c.

Referenced by read_decode_convert_and_store().

◆ read_decode_convert_and_store()

static int read_decode_convert_and_store	(	AVAudioFifo *	fifo,
		AVFormatContext *	input_format_context,
		AVCodecContext *	input_codec_context,
		AVCodecContext *	output_codec_context,
		SwrContext *	resampler_context,
		int *	finished
	)

static

Read one audio frame from the input file, decode, convert and store it in the FIFO buffer.

Parameters

	fifo	Buffer used for temporary storage
	input_format_context	Format context of the input file
	input_codec_context	Codec context of the input file
	output_codec_context	Codec context of the output file
	resampler_context	Resample context for the conversion
[out]	finished	Indicates whether the end of file has been reached and all data has been decoded. If this flag is false, there is more data to be decoded, i.e., this function has to be called again.

Returns: Error code (0 if successful)

Examples: transcode_aac.c.

Definition at line 552 of file transcode_aac.c.

Referenced by main().

◆ init_output_frame()

static int init_output_frame	(	AVFrame **	frame,
		AVCodecContext *	output_codec_context,
		int	frame_size
	)

static

Initialize one input frame for writing to the output file.

The frame will be exactly frame_size samples large.

Parameters

[out]	frame	Frame to be initialized
	output_codec_context	Codec context of the output file
	frame_size	Size of the frame

Returns: Error code (0 if successful)

Examples: transcode_aac.c.

Definition at line 619 of file transcode_aac.c.

Referenced by load_encode_and_write().

◆ encode_audio_frame()

static int encode_audio_frame	(	AVFrame *	frame,
		AVFormatContext *	output_format_context,
		AVCodecContext *	output_codec_context,
		int *	data_present
	)

static

Encode one frame worth of audio to the output file.

Parameters

	frame	Samples to be encoded
	output_format_context	Format context of the output file
	output_codec_context	Codec context of the output file
[out]	data_present	Indicates whether data has been encoded

Returns: Error code (0 if successful)

Examples: transcode_aac.c.

Definition at line 665 of file transcode_aac.c.

Referenced by load_encode_and_write(), and main().

◆ load_encode_and_write()

static int load_encode_and_write	(	AVAudioFifo *	fifo,
		AVFormatContext *	output_format_context,
		AVCodecContext *	output_codec_context
	)

static

Load one audio frame from the FIFO buffer, encode and write it to the output file.

Parameters

fifo	Buffer used for temporary storage
output_format_context	Format context of the output file
output_codec_context	Codec context of the output file

Returns: Error code (0 if successful)

Examples: transcode_aac.c.

Definition at line 737 of file transcode_aac.c.

Referenced by main().

◆ write_output_file_trailer()

static int write_output_file_trailer ( AVFormatContext * output_format_context )

static

Write the trailer of the output file container.

Parameters

output_format_context Format context of the output file

Returns: Error code (0 if successful)

Examples: transcode_aac.c.

Definition at line 777 of file transcode_aac.c.

Referenced by main().

◆ main()

int main	(	int	argc,
		char **	argv
	)

Examples: transcode_aac.c.

Definition at line 788 of file transcode_aac.c.

Variable Documentation

◆ pts

int64_t pts = 0

static

Examples: transcode_aac.c.

Definition at line 654 of file transcode_aac.c.

Referenced by encode_audio_frame().

Macros

Functions

Variables

Detailed Description

Macro Definition Documentation

◆ OUTPUT_BIT_RATE

◆ OUTPUT_CHANNELS

Function Documentation

◆ open_input_file()

◆ open_output_file()

◆ init_packet()

◆ init_input_frame()

◆ init_resampler()

◆ init_fifo()

◆ write_output_file_header()

◆ decode_audio_frame()

◆ init_converted_samples()

◆ convert_samples()

◆ add_samples_to_fifo()

◆ read_decode_convert_and_store()

◆ init_output_frame()

◆ encode_audio_frame()

◆ load_encode_and_write()

◆ write_output_file_trailer()

◆ main()

Variable Documentation

◆ pts