diff options
author | Michael Niedermayer <michaelni@gmx.at> | 2013-11-27 13:30:37 +0400 |
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committer | Michael Niedermayer <michaelni@gmx.at> | 2013-11-27 13:31:08 +0400 |
commit | 715f3623f8cd16c9e8d704bad45b76aa30d31cd2 (patch) | |
tree | d69db24220cb75d3e77561453e0c21cf8ff783a2 /doc/examples/transcode_aac.c | |
parent | 3aaa50a9972c9f350ad9ce6decf3ecb2aaffa84a (diff) | |
parent | 10421bcf0ab5d48fa3d84de803e657b77fe7d3c0 (diff) |
Merge remote-tracking branch 'qatar/master'
* qatar/master:
Add an audio transcoding example.
Conflicts:
configure
doc/Makefile
Merged-by: Michael Niedermayer <michaelni@gmx.at>
Diffstat (limited to 'doc/examples/transcode_aac.c')
-rw-r--r-- | doc/examples/transcode_aac.c | 769 |
1 files changed, 769 insertions, 0 deletions
diff --git a/doc/examples/transcode_aac.c b/doc/examples/transcode_aac.c new file mode 100644 index 0000000000..17d80fe8f9 --- /dev/null +++ b/doc/examples/transcode_aac.c @@ -0,0 +1,769 @@ +/* + * 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 + */ + +/** + * @file simple audio converter + * Convert an input audio file to AAC in an MP4 container using Libav. + * @author Andreas Unterweger (dustsigns@gmail.com) + */ + +#include <stdio.h> + +#include "libavformat/avformat.h" +#include "libavformat/avio.h" + +#include "libavcodec/avcodec.h" + +#include "libavutil/audio_fifo.h" +#include "libavutil/avstring.h" +#include "libavutil/frame.h" +#include "libavutil/opt.h" + +#include "libavresample/avresample.h" + +/** 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)); + *input_format_context = NULL; + 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)); + avformat_close_input(input_format_context); + 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"); + goto cleanup; + } + + av_strlcpy((*output_format_context)->filename, filename, + sizeof((*output_format_context)->filename)); + + /** Find the encoder to be used by its name. */ + if (!(output_codec = avcodec_find_encoder(AV_CODEC_ID_AAC))) { + fprintf(stderr, "Could not find an AAC encoder.\n"); + goto cleanup; + } + + /** 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"); + error = AVERROR(ENOMEM); + goto cleanup; + } + + /** 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)->channel_layout = av_get_default_channel_layout(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)); + goto cleanup; + } + + return 0; + +cleanup: + avio_close((*output_format_context)->pb); + avformat_free_context(*output_format_context); + *output_format_context = NULL; + return error < 0 ? error : AVERROR_EXIT; +} + +/** 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 = av_frame_alloc())) { + fprintf(stderr, "Could not allocate input frame\n"); + return AVERROR(ENOMEM); + } + 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; +} + +/** 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, int *finished) +{ + /** 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) { + /** If we are the the end of the file, flush the decoder below. */ + if (error == AVERROR_EOF) + *finished = 1; + else { + 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 we are at the end of the file, pass an empty packet to the decoder + * to flush it. + */ + 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)); + av_free_packet(&input_packet); + return error; + } + + /** + * If the decoder has not been flushed completely, we are not finished, + * so that this function has to be called again. + */ + if (*finished && *data_present) + *finished = 0; + av_free_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; +} + +/** + * 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 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, finished)) + goto cleanup; + /** + * If we are at the end of the file and there are no more samples + * in the decoder which are delayed, we are actually finished. + * This must not be treated as an error. + */ + if (*finished && !data_present) { + ret = 0; + goto cleanup; + } + /** If there is decoded data, convert and store it */ + if (data_present) { + /** Initialize the temporary storage for the converted input samples. */ + if (init_converted_samples(&converted_input_samples, output_codec_context, + input_frame->nb_samples)) + 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->extended_data, converted_input_samples, + input_frame->nb_samples, 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->nb_samples)) + goto cleanup; + ret = 0; + } + ret = 0; + +cleanup: + if (converted_input_samples) { + av_freep(&converted_input_samples[0]); + free(converted_input_samples); + } + av_frame_free(&input_frame); + + return ret; +} + +/** + * 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) +{ + int error; + + /** Create a new frame to store the audio samples. */ + if (!(*frame = av_frame_alloc())) { + fprintf(stderr, "Could not allocate output frame\n"); + return AVERROR_EXIT; + } + + /** + * Set the frame's parameters, especially its size and format. + * av_frame_get_buffer needs this to allocate memory for the + * audio samples of the frame. + * Default channel layouts based on the number of channels + * are assumed for simplicity. + */ + (*frame)->nb_samples = frame_size; + (*frame)->channel_layout = output_codec_context->channel_layout; + (*frame)->format = output_codec_context->sample_fmt; + (*frame)->sample_rate = output_codec_context->sample_rate; + + /** + * Allocate the samples of the created frame. This call will make + * sure that the audio frame can hold as many samples as specified. + */ + if ((error = av_frame_get_buffer(*frame, 0)) < 0) { + fprintf(stderr, "Could allocate output frame samples (error '%s')\n", + get_error_text(error)); + av_frame_free(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)); + av_free_packet(&output_packet); + return error; + } + + /** Write one audio frame from the temporary packet to the output file. */ + if (*data_present) { + if ((error = av_write_frame(output_format_context, &output_packet)) < 0) { + fprintf(stderr, "Could not write frame (error '%s')\n", + get_error_text(error)); + av_free_packet(&output_packet); + return error; + } + + av_free_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 = FFMIN(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"); + av_frame_free(&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)) { + av_frame_free(&output_frame); + return AVERROR_EXIT; + } + av_frame_free(&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 audio file to an AAC file in an MP4 container. */ +int main(int argc, char **argv) +{ + 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; + + if (argc < 3) { + fprintf(stderr, "Usage: %s <input file> <output file>\n", argv[0]); + exit(1); + } + + /** Register all codecs and formats so that they can be used. */ + av_register_all(); + /** Open the input file for reading. */ + if (open_input_file(argv[1], &input_format_context, + &input_codec_context)) + goto cleanup; + /** Open the output file for writing. */ + if (open_output_file(argv[2], 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) { + int data_written; + /** Flush the encoder as it may have delayed frames. */ + do { + if (encode_audio_frame(NULL, output_format_context, + output_codec_context, &data_written)) + goto cleanup; + } while (data_written); + 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) { + avio_close(output_format_context->pb); + avformat_free_context(output_format_context); + } + if (input_codec_context) + avcodec_close(input_codec_context); + if (input_format_context) + avformat_close_input(&input_format_context); + + return ret; +} |