avcodec_decode_audio2返回值为-1?

我用ffmpeg4.0版本代替旧版本3.2时,解码时发现avcodec_decode_audio2返回值总为-1,我程序中代码如下:

         int out_size = AVCODEC_MAX_AUDIO_FRAME_SIZE;
	uint8_t * inbuf = (uint8_t *)malloc(out_size);
	FILE* pFileWav;
	int fileSize; 
	pFileWav= fopen("b.pcm","wb+");
	while(av_read_frame(pFormatCtx, &packet)>=0)
	{
		if(packet.stream_index==audioStream) {
			pktdata = packet.data;
			pktsize = packet.size;
			while(pktsize>0)
			{
				//解码
				int len=avcodec_decode_audio2(pCodecCtx,(int16_t *)inbuf,&out_size,pktdata,pktsize);
//				int len=avcodec_decode_audio3(pCodecCtx,(int16_t *)inbuf,&out_size,&packet);
				if (len<0)
				{
					printf("Error while decoding.\n");
					break;
				}
				if(out_size>0)
				{
					fwrite(inbuf,1,out_size,pFileWav);//pcm记录
					fflush(pFileWav);
					fileSize += out_size;
				}
				pktsize -= len;
				pktdata += len;
			}
		}   
		av_free_packet(&packet);
	} 


 

后来查了下ffmpeg3.2源代码,发现:

int attribute_align_arg avcodec_decode_audio2(AVCodecContext *avctx, int16_t *samples,
                         int *frame_size_ptr,
                         const uint8_t *buf, int buf_size)
{
    int ret;

    if((avctx->codec->capabilities & CODEC_CAP_DELAY) || buf_size){
        //FIXME remove the check below _after_ ensuring that all audio check that the available space is enough
        if(*frame_size_ptr < AVCODEC_MAX_AUDIO_FRAME_SIZE){
            av_log(avctx, AV_LOG_ERROR, "buffer smaller than AVCODEC_MAX_AUDIO_FRAME_SIZE\n");
            return -1;
        }
        if(*frame_size_ptr < FF_MIN_BUFFER_SIZE ||
        *frame_size_ptr < avctx->channels * avctx->frame_size * sizeof(int16_t)){
            av_log(avctx, AV_LOG_ERROR, "buffer %d too small\n", *frame_size_ptr);
            return -1;
        }

        ret = avctx->codec->decode(avctx, samples, frame_size_ptr,
                                buf, buf_size);
        avctx->frame_number++;
    }else{
        ret= 0;
        *frame_size_ptr=0;
    }
    return ret;
}

#if LIBAVCODEC_VERSION_INT < ((52<<16)+(0<<8)+0)
int avcodec_decode_audio(AVCodecContext *avctx, int16_t *samples,
                         int *frame_size_ptr,
                         const uint8_t *buf, int buf_size){
    *frame_size_ptr= AVCODEC_MAX_AUDIO_FRAME_SIZE;
    return avcodec_decode_audio2(avctx, samples, frame_size_ptr, buf, buf_size);
}
#endif


 

ffmpeg4.0中代码为:

int attribute_align_arg avcodec_decode_audio2(AVCodecContext *avctx, int16_t *samples,
                         int *frame_size_ptr,
                         const uint8_t *buf, int buf_size)
{
    AVPacket avpkt;
    av_init_packet(&avpkt);
    avpkt.data = buf;
    avpkt.size = buf_size;

    return avcodec_decode_audio3(avctx, samples, frame_size_ptr, &avpkt);
}
#endif

int attribute_align_arg avcodec_decode_audio3(AVCodecContext *avctx, int16_t *samples,
                         int *frame_size_ptr,
                         AVPacket *avpkt)
{
    int ret;

    if((avctx->codec->capabilities & CODEC_CAP_DELAY) || avpkt->size){
        //FIXME remove the check below _after_ ensuring that all audio check that the available space is enough
        if(*frame_size_ptr < AVCODEC_MAX_AUDIO_FRAME_SIZE){
            av_log(avctx, AV_LOG_ERROR, "buffer smaller than AVCODEC_MAX_AUDIO_FRAME_SIZE\n");
            return -1;
        }
        if(*frame_size_ptr < FF_MIN_BUFFER_SIZE ||
        *frame_size_ptr < avctx->channels * avctx->frame_size * sizeof(int16_t)){
            av_log(avctx, AV_LOG_ERROR, "buffer %d too small\n", *frame_size_ptr);
            return -1;
        }

        ret = avctx->codec->decode(avctx, samples, frame_size_ptr, avpkt);
        avctx->frame_number++;
    }else{
        ret= 0;
        *frame_size_ptr=0;
    }
    return ret;
}

 

即每次调用avcodec_decode_audio2时,若(*frame_size_ptr < AVCODEC_MAX_AUDIO_FRAME_SIZE),则返回值为-1,后来我就顺着这个思路,往上找,过不其然,发现了问题之所在,原因是:在intlen=avcodec_decode_audio2(pCodecCtx,(int16_t *)inbuf,&out_size,pktdata,pktsize)处理后,out_size的值变为4608,而不是AVCODEC_MAX_AUDIO_FRAME_SIZE,所以在4.0中,*frame_size_ptr < AVCODEC_MAX_AUDIO_FRAME_SIZE,返回值自然为-1

找到了问题,解决自然容易,要么在ffmpeg源码处该,要么在客户端,而我选择了后者,主要是方便:

int out_size = AVCODEC_MAX_AUDIO_FRAME_SIZE;
	uint8_t * inbuf = (uint8_t *)malloc(out_size);

	FILE* pFileWav;
	int fileSize; 
	pFileWav= fopen("b.pcm","wb+");
	while(av_read_frame(pFormatCtx, &packet)>=0)
	{
		if(packet.stream_index==audioStream) {
			pktdata = packet.data;
			pktsize = packet.size;
			out_size=AVCODEC_MAX_AUDIO_FRAME_SIZE;//加这句就ok了
			while(pktsize>0)
			{
				//解码
				int len=avcodec_decode_audio2(pCodecCtx,(int16_t *)inbuf,&out_size,pktdata,pktsize);
//				int len=avcodec_decode_audio3(pCodecCtx,(int16_t *)inbuf,&out_size,&packet);
				if (len<0)
				{
					printf("Error while decoding.\n");
					break;
				}
				if(out_size>0)
				{
					fwrite(inbuf,1,out_size,pFileWav);//pcm记录
					fflush(pFileWav);
					fileSize += out_size;
				}
				pktsize -= len;
				pktdata += len;
			}
		}   
		av_free_packet(&packet);
	}   
	avcodec_close(pCodecCtx);
	av_close_input_file(pFormatCtx);
	return TRUE;
}

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