解码MP3文件是将MP3格式的音频文件转换为可以播放的音频格式,如WAV或者AAC。以下是一个简单的步骤来解码MP3文件:
以下是一个使用FFmpeg解码MP3文件的示例代码:
#include<stdio.h>
#include <stdlib.h>
#include<string.h>
#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include <libswresample/swresample.h>
int main(int argc, char *argv[]) {
if (argc != 3) {
printf("Usage: %s input_file output_file\n", argv[0]);
return 1;
}
const char *input_file = argv[1];
const char *output_file = argv[2];
// Initialize FFmpeg
av_register_all();
avformat_network_init();
// Open input file
AVFormatContext *input_format_context = avformat_alloc_context();
if (avformat_open_input(&input_format_context, input_file, NULL, NULL) != 0) {
printf("Could not open input file\n");
return 1;
}
// Find audio stream
int audio_stream_index = -1;
for (int i = 0; i< input_format_context->nb_streams; i++) {
if (input_format_context->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_AUDIO) {
audio_stream_index = i;
break;
}
}
if (audio_stream_index == -1) {
printf("Could not find audio stream\n");
return 1;
}
// Get audio codec parameters
AVCodecParameters *audio_codec_parameters = input_format_context->streams[audio_stream_index]->codecpar;
// Find audio decoder
AVCodec *audio_codec = avcodec_find_decoder(audio_codec_parameters->codec_id);
if (audio_codec == NULL) {
printf("Could not find audio decoder\n");
return 1;
}
// Open audio codec context
AVCodecContext *audio_codec_context = avcodec_alloc_context3(audio_codec);
if (avcodec_parameters_to_context(audio_codec_context, audio_codec_parameters) < 0) {
printf("Could not open audio codec context\n");
return 1;
}
// Initialize audio codec context
if (avcodec_open2(audio_codec_context, audio_codec, NULL) < 0) {
printf("Could not initialize audio codec context\n");
return 1;
}
// Open output file
FILE *output_file_pointer = fopen(output_file, "wb");
if (output_file_pointer == NULL) {
printf("Could not open output file\n");
return 1;
}
// Decode audio frames
AVPacket packet;
av_init_packet(&packet);
while (av_read_frame(input_format_context, &packet) == 0) {
if (packet.stream_index == audio_stream_index) {
AVFrame *frame = av_frame_alloc();
int result = avcodec_send_packet(audio_codec_context, &packet);
while (result >= 0) {
result = avcodec_receive_frame(audio_codec_context, frame);
if (result == 0) {
// Convert audio frame to PCM format
SwrContext *resample_context = swr_alloc();
resample_context = swr_alloc_set_opts(resample_context, AV_CH_LAYOUT_STEREO, AV_SAMPLE_FMT_S16, 44100, frame->channel_layout, frame->format, frame->sample_rate, 0, NULL);
swr_init(resample_context);
uint8_t *output_buffer = (uint8_t *)av_malloc(44100 * 2 * sizeof(int16_t));
int output_size = swr_convert(resample_context, &output_buffer, 44100 * 2, (const uint8_t **)frame->data, frame->nb_samples);
fwrite(output_buffer, 1, output_size * 2 * sizeof(int16_t), output_file_pointer);
av_free(output_buffer);
swr_free(&resample_context);
}
}
av_frame_free(&frame);
}
av_packet_unref(&packet);
}
// Close files and release resources
fclose(output_file_pointer);
avcodec_close(audio_codec_context);
avformat_close_input(&input_format_context);
avformat_network_deinit();
return 0;
}
这个示例代码使用FFmpeg库解码MP3文件,并将其转换为WAV格式。你可以根据自己的需求进行修改和优化。
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