封装好的 ffmpeg 转换音频文件格式的 DLL

http://download.youkuaiyun.com/source/1021257

 

这两天因为项目需要研究了一下 ffmpeg，非常强大，顺便把我做的音频转换的代码发上来，我们的项目需要是从 wav 转成 44k hz flv，我测试了mp3转换也都是成功的，相信转别的一些常用格式也没问题。

 

09/02/23 注：上面下载连接里的代码有点问题，不支持转换不同的采样率，所以我后来重写了，网上关于ffmpeg 的代码很少，看大家大多数都是参考ffmpeg自带的例子，实际上ffmpeg自身控制台程序的代码是可以搞定一切的，不过代码稍微有点复杂需要花点时间研究，下面是我写的代码，封装了一个 DLL只导出一个函数，参数就不多解释了：

int ConverAudio(const char* input_file, const char* output_file, int samples_rate, int channel);

 

代码如下：

 

int ffmpeg_conver_audio(const char* input_file, const char* output_file, int samples_rate, int channel) { AVFormatContext *infmt_ctx; int i = 0; 初始化 avcodec_register_all(); avdevice_register_all(); av_register_all(); 输入 infmt_ctx = av_alloc_format_context(); //打开输入文件 if(av_open_input_file(&infmt_ctx, input_file, NULL, 0, NULL)!=0) { debug_string("can't open input file/n"); return -1; } //取出流信息 if(av_find_stream_info(infmt_ctx) <0) { debug_string("can't find suitable codec parameters/n"); return -2; } //dump_format(infmt_ctx, 0, input_file, 0); //列出输入文件的相关流信息 // 查找音频流信息 int audioindex=-1; for(unsigned int j = 0; j < infmt_ctx->nb_streams; j++) { if(infmt_ctx->streams[j]->codec->codec_type == CODEC_TYPE_AUDIO) { audioindex=j; break; } } if(audioindex == -1) //没有找到音频流 { debug_string("can't find audio stream/n"); return -3; } AVCodecContext *incode_ctx; AVCodec *incodec; incode_ctx = infmt_ctx->streams[audioindex]->codec; //找到合适的音频解码器 incodec = avcodec_find_decoder(incode_ctx->codec_id); if(incodec == NULL) { debug_string("can't find suitable audio decoder/n"); return -4; } //打开该音频解码器 if(avcodec_open(incode_ctx, incodec) < 0) { debug_string("can't open the audio decoder/n"); return -5; } 输出 /* 解析输出文件的格式 */ AVOutputFormat *outfmt = guess_format(NULL, output_file, NULL); if (!outfmt) { printf("Could not deduce output format from file extension: using MPEG./n"); outfmt = guess_format("mpeg", NULL, NULL); } if (!outfmt) { debug_string("Could not find suitable output format/n"); return -6; } outfmt->audio_codec = CODEC_ID_MP3; /* allocate the output media context */ AVFormatContext *outfmt_ctx = av_alloc_format_context(); if (!outfmt_ctx) { debug_string("Memory error/n"); return -7; } /* 保存输出文件的格式 */ outfmt_ctx->oformat = outfmt; snprintf(outfmt_ctx->filename, sizeof(outfmt_ctx->filename), "%s", output_file); /* add the audio and video streams using the default format codecs and initialize the codecs */ /* 输出文件的视频流编码器ID */ AVCodecContext *outcode_ctx; AVCodec *outcodec; AVStream *audio_st = NULL/*, *video_st*/; //double audio_pts, video_pts; //if (outfmt->video_codec != CODEC_ID_NONE) { // video_st = add_video_stream(outfmt_ctx, outfmt->video_codec); //} /* 输出文件的音频流编码器ID */ if (outfmt->audio_codec != CODEC_ID_NONE) { audio_st = av_new_stream(outfmt_ctx, 1); outcode_ctx = audio_st->codec; outcode_ctx->codec_id = outfmt->audio_codec; outcode_ctx->codec_type = CODEC_TYPE_AUDIO; //oAcc->bit_rate =inCodecCtx->bit_rate ; outcode_ctx->sample_rate = samples_rate > 0 ? samples_rate : incode_ctx->sample_rate; //outcode_ctx->time_base.den = 1; //outcode_ctx->time_base.num = outcode_ctx->sample_rate; outcode_ctx->channels = channel > 0 ? channel : incode_ctx->channels; outcode_ctx->block_align = incode_ctx->block_align; if(outcode_ctx->block_align == 1 && outcode_ctx->codec_id == CODEC_ID_MP3) outcode_ctx->block_align = 0; } /* 设置输出参数 */ if (av_set_parameters(outfmt_ctx, NULL) < 0) { debug_string("Invalid output format parameters/n"); return -8; } /* 列出输出文件的格式信息 */ dump_format(outfmt_ctx, 0, output_file, 1); strcpy(outfmt_ctx->title, infmt_ctx->title); strcpy(outfmt_ctx->author, infmt_ctx->author); strcpy(outfmt_ctx->copyright, infmt_ctx->copyright); strcpy(outfmt_ctx->comment, infmt_ctx->comment); strcpy(outfmt_ctx->album, infmt_ctx->album); outfmt_ctx->year = infmt_ctx->year; outfmt_ctx->track = infmt_ctx->track; strcpy(outfmt_ctx->genre, infmt_ctx->genre); //dump_format(oc,0,output_file_name,1);//列出输出文件的相关流信息 //找到合适的音频编码器 outcodec = avcodec_find_encoder(outfmt_ctx->oformat->audio_codec);//(CODEC_ID_AAC); if(!outcodec) { debug_string("can't find suitable audio encoder/n"); return -9; } if(avcodec_open(outcode_ctx, outcodec) <0) // { debug_string("can't open the output audio codec"); return -10; } /* now that all the parameters are set, we can open the audio and video codecs and allocate the necessary encode buffers */ //if (video_st) // open_video(outfmt_ctx, video_st); /* 打开音频编码器 */ /* int audioSize = 128 * 1024 * 4; //AVCODEC_MAX_AUDIO_FRAME_SIZE;//audio_outbuf_size/incode_ctx->channels; if (outcode_ctx->frame_size <= 1) { switch(outcode_ctx->codec_id) { case CODEC_ID_PCM_S32LE: case CODEC_ID_PCM_S32BE: case CODEC_ID_PCM_U32LE: case CODEC_ID_PCM_U32BE: audioSize <<= 1; break; case CODEC_ID_PCM_S24LE: case CODEC_ID_PCM_S24BE: case CODEC_ID_PCM_U24LE: case CODEC_ID_PCM_U24BE: case CODEC_ID_PCM_S24DAUD: audioSize = audioSize / 2 * 3; break; case CODEC_ID_PCM_S16LE: case CODEC_ID_PCM_S16BE: case CODEC_ID_PCM_U16LE: case CODEC_ID_PCM_U16BE: break; default: audioSize >>= 1; break; } outSampleSize = audioSize * 2 * outcode_ctx->channels; } else { outSampleSize = outcode_ctx->frame_size * 2 * outcode_ctx->channels; } */ /* 如果输出文件不存在, 则创建输出文件 */ if (!(outfmt->flags & AVFMT_NOFILE)) { if (url_fopen(&outfmt_ctx->pb, output_file, URL_WRONLY) < 0) { debug_string("Could not open '%s'/n", output_file); return -11; } } int ret = 0; uint8_t* outbuf; uint8_t* audiobuf; uint8_t* resamplebuf; uint8_t* databuf; int outbuf_len = AVCODEC_MAX_AUDIO_FRAME_SIZE;; int audiobuf_len = AVCODEC_MAX_AUDIO_FRAME_SIZE; int resamplebuf_len = AVCODEC_MAX_AUDIO_FRAME_SIZE; int64_t pt; outbuf = (uint8_t*)av_malloc(outbuf_len); audiobuf = (uint8_t*)av_malloc(audiobuf_len); resamplebuf = (uint8_t*)av_malloc(resamplebuf_len); databuf = (uint8_t*)av_malloc(AVCODEC_MAX_AUDIO_FRAME_SIZE); AVFifoBuffer fifo; av_fifo_init(&fifo, av_fifo_size(&fifo)+AVCODEC_MAX_AUDIO_FRAME_SIZE); ReSampleContext* resample = audio_resample_init(outcode_ctx->channels, incode_ctx->channels, outcode_ctx->sample_rate, incode_ctx->sample_rate); av_write_header(outfmt_ctx); AVPacket packet; while(av_read_frame(infmt_ctx, &packet) >= 0) { pt = packet.pts; if(outcode_ctx->codec_id != CODEC_ID_NONE && packet.stream_index == audio_st->index) { if(incode_ctx->codec_id == outcode_ctx->codec_id && incode_ctx->sample_rate == outcode_ctx->sample_rate && incode_ctx->channels == incode_ctx->channels) { av_write_frame(outfmt_ctx, &packet); } else { if (packet.size > 0) { avcodec_decode_audio(incode_ctx, (short *)audiobuf, &audiobuf_len, packet.data, packet.size); if(incode_ctx->sample_rate != outcode_ctx->sample_rate || incode_ctx->channels != outcode_ctx->channels) { // resample the audio resamplebuf_len = audio_resample(resample, (short*)resamplebuf, (short*)audiobuf, audiobuf_len / (incode_ctx->channels * 2)); //av_fifo_realloc(&fifo, av_fifo_size(&fifo)+audiobuf_len); av_fifo_write(&fifo, resamplebuf, resamplebuf_len * outcode_ctx->channels * 2); } else { //av_fifo_realloc(&fifo, av_fifo_size(&fifo)+audiobuf_len); av_fifo_write(&fifo, audiobuf, audiobuf_len); } if(audiobuf_len > 0) { int frame_bytes = outcode_ctx->frame_size * 2 * outcode_ctx->channels; while(av_fifo_read(&fifo, databuf, frame_bytes) == 0) { AVPacket pkt; av_init_packet(&pkt); pkt.size = avcodec_encode_audio(outcode_ctx, outbuf, outbuf_len, (short*)databuf); if (outcode_ctx->coded_frame && outcode_ctx->coded_frame->pts != AV_NOPTS_VALUE) pkt.pts = av_rescale_q(outcode_ctx->coded_frame->pts, outcode_ctx->time_base, audio_st->time_base); pkt.stream_index = audio_st->index; pkt.data = outbuf; pkt.flags |= PKT_FLAG_KEY; // write the compressed frame in the media file if (pkt.size > 0) { ret = av_write_frame(outfmt_ctx, &pkt); } av_free_packet(&pkt); } } } //End if } } av_free_packet(&packet); } av_fifo_free(&fifo); /* write the trailer, if any */ av_write_trailer(outfmt_ctx); av_free(outbuf); av_free(audiobuf); av_free(resamplebuf); av_free(databuf); audio_resample_close(resample); avcodec_close(outcode_ctx); /* free the streams */ for(i = 0; i < outfmt_ctx->nb_streams; i++) { av_freep(&outfmt_ctx->streams[i]->codec); av_freep(&outfmt_ctx->streams[i]); } if (!(outfmt->flags & AVFMT_NOFILE)) { /* close the output file */ url_fclose(outfmt_ctx->pb); } av_free(outfmt_ctx); avcodec_close(incode_ctx); av_close_input_file(infmt_ctx); return ret; }