ffmpeg提取aac数据
方法1:通过命令提取
ffmpeg -i input.mp4 -vn -acodec aac ../output.aac
方法2:通过代码提取
流程图
main.c
#include "libavutil/log.h" #include "libavformat/avformat.h" #include "libavutil/avutil.h" static int get_audio_obj_type(int aac_type) { //AAC HE V2 = AAC LC + SBR + PS //AAV HE = AAC LC + SBR //所以无论是 AAC_HEv2 还是 AAC_HE 都是 AAC_LC if (aac_type == 0 || aac_type == 2 || aac_type == 3) { return aac_type + 1; } else { return 2; } } static int get_sample_rate_index(int freq, int aac_type) { int i; int freq_arr[13] = { 96000, 88200, 64000, 48000, 44100, 32000, 24000, 22050, 16000, 12000, 11025, 8000, 7350 }; //如果是 AAC HEv2 或 AAC HE, 则频率减半 if (aac_type == 28 || aac_type == 4) { freq /= 2; } for (i = 0; i < 13; i++) { if (freq == freq_arr[i]) { return i; } } return 4;//默认是44100 } static int get_channel_config(int channels, int aac_type) { //如果是 AAC HEv2 通道数减半 if (aac_type == 28) { return (channels / 2); } return channels; } void getADTSHeader(uint8_t *adtsHeader, int packetSize, int profile, int sampleRate, int channels) { int audio_object_type = get_audio_obj_type(profile); int sampling_frequency_index = get_sample_rate_index(sampleRate, profile); int channel_config = get_channel_config(channels, profile); int adtsLen = packetSize + 7; adtsHeader[0] = 0xff; //高8bits adtsHeader[1] = 0xf0; //低4bits adtsHeader[1] |= (0 << 3); //MPEG Version:0 for MPEG-4,1 for MPEG-2 1bit adtsHeader[1] |= (0 << 1); //Layer:0 2bits adtsHeader[1] |= 1; //protection absent:1 1bit adtsHeader[2] = (audio_object_type - 1) << 6; //profile:audio_object_type - 1 2bits adtsHeader[2] |= (sampling_frequency_index & 0x0f) << 2; //sampling frequency index:sampling_frequency_index 4bits adtsHeader[2] |= (0 << 1); //private bit:0 1bit adtsHeader[2] |= (channel_config & 0x04) >> 2; //channel configuration:channel_config 高1bit adtsHeader[3] = (channel_config & 0x03) << 6; //channel configuration:channel_config 低2bits adtsHeader[3] |= (0 << 5); //original:0 1bit adtsHeader[3] |= (0 << 4); //home:0 1bit adtsHeader[3] |= (0 << 3); //copyright id bit:0 1bit adtsHeader[3] |= (0 << 2); //copyright id start:0 1bit adtsHeader[3] |= ((adtsLen & 0x1800) >> 11); //frame length:value 高2bits adtsHeader[4] = (uint8_t) ((adtsLen & 0x7f8) >> 3); //frame length:value 中间8bits adtsHeader[5] = (uint8_t) ((adtsLen & 0x7) << 5); //frame length:value 低3bits adtsHeader[5] |= 0x1f; //buffer fullness:0x7ff 高5bits adtsHeader[6] = 0xfc; } int main(int argc, char **argv) { av_log_set_level(AV_LOG_DEBUG); if (argc < 3) { av_log(NULL, AV_LOG_ERROR, "Usage: %s inputFile outputFile\n", argv[0]); return -1; } const char *inputFile = argv[1]; const char *outputFile = argv[2]; AVFormatContext *fCtx = NULL; int ret = avformat_open_input(&fCtx, inputFile, NULL, NULL); if (ret != 0) { av_log(NULL, AV_LOG_ERROR, "Open input file %s failed: %s\n", inputFile, av_err2str(ret)); return -1; } ret = avformat_find_stream_info(fCtx, NULL); if (ret < 0) { av_log(NULL, AV_LOG_ERROR, "Find input file stream info failed: %s\n", av_err2str(ret)); avformat_close_input(&fCtx); return -1; } int audioIndex = av_find_best_stream(fCtx, AVMEDIA_TYPE_AUDIO, -1, -1, NULL, 0); if (audioIndex < 0) { av_log(NULL, AV_LOG_ERROR, "Find best stream failed: %d\n", audioIndex); avformat_close_input(&fCtx); return -1; } av_log(NULL, AV_LOG_INFO, "audioIndex=%d\n", audioIndex); FILE *dst = fopen(outputFile, "wb"); if (dst == NULL) { av_log(NULL, AV_LOG_ERROR, "Open output file: %s failed\n", outputFile); avformat_close_input(&fCtx); return -1; } AVPacket *packet = av_packet_alloc(); packet->data = NULL; packet->size = 0; while (av_read_frame(fCtx, packet) == 0) { if (packet->stream_index == audioIndex) { uint8_t header[7] = {0}; getADTSHeader(header, packet->size, fCtx->streams[audioIndex]->codecpar->profile, fCtx->streams[audioIndex]->codecpar->sample_rate, fCtx->streams[audioIndex]->codecpar->channels); size_t size = fwrite(header, sizeof(uint8_t), sizeof(header), dst); if (size != sizeof(header)) { av_log(NULL, AV_LOG_ERROR, "Write ADTS header size: %zu, expected size: %lu\n", size, sizeof(header)); fclose(dst); avformat_close_input(&fCtx); return -1; } size = fwrite(packet->data, sizeof(uint8_t), packet->size, dst); if (size != packet->size) { av_log(NULL, AV_LOG_ERROR, "Write size: %zu, packet size: %d\n", size, packet->size); fclose(dst); avformat_close_input(&fCtx); return -1; } } av_packet_unref(packet); } if (fCtx != NULL) { avformat_close_input(&fCtx); } fclose(dst); return 0; }
Makefile
TARGET=main SRC=main.c CC=gcc CFLAGS=-I /usr/local/ffmpeg/include LDFLAGS=-L /usr/local/ffmpeg/lib LDFLAGS+= -lavutil -lavformat -lavcodec all:$(TARGET) $(TARGET):$(SRC) $(CC) $(SRC) $(CFLAGS) $(LDFLAGS) -o $(TARGET) clean: rm -rf $(TARGET)