首页 > 编程学习 > FFmepg-8、视频编码相关,遇到2个问题未解决

基于FFMPEG的视频编码器。该编码器实现了YUV420P的像素数据编码为H.264的压缩编码数据,或编码成其他文件也是类似的操作。

主要操作是读取原来的YUV数据压缩到文件中并且写入文件头尾,

存在的两个问题暂时先记录
1、avcodec_receive_packet的时候总是提示EAGAIN错误,而使用旧的avcodec_encode_video2却可以编码
2、ffmpeg自带的exmple中的encode_video.c要如何运行,

相关函数和要注意的地方
第1步、就是得到AVOutputFormat* fmt;输出格式

有两种方法
//Method1.
pFormatCtx = avformat_alloc_context();
//av_guess_format在注册输出格式列表中返回与所提供的参数最匹配的输出格式,如果没有匹配则返回NULL。
//AVOutputFormat *av_guess_format(const char *short_name,   const char *filename, const char *mime_type);
//从前往后去匹配 如果为NULL则选择后一个参数
fmt = av_guess_format(NULL, out_file, NULL);//根据文件名去匹配输出格式AVOutputFormat
pFormatCtx->oformat = fmt;

//Method 2.
//为输出格式分配一个AVFormatContext。
//int avformat_alloc_output_context2(AVFormatContext **ctx, AVOutputFormat *oformat,const char *format_name, const char *filename);
//oformat用于分配上下文的格式,如果为NULL则用format_name、filename代替
//format_name用于分配上下文的输出格式的名称,如果为NULL则使用filename文件名代替
//filename用于分配上下文的文件名
avformat_alloc_output_context2(&pFormatCtx, NULL, NULL, out_file);
fmt = pFormatCtx->oformat;

第2步、实例化AVIOContext与输出文件进行绑定

//创建并初始化一个AVIOContext,用于访问url指示的资源。
原型;传入双重指针,填充AVIOContext 
int avio_open(AVIOContext **s, const char *url, int flags);
使用
if (avio_open(&pFormatCtx->pb, out_file, AVIO_FLAG_READ_WRITE) < 0) {
	printf("Failed to open output file! \n");
	return -1;
}

第3步、创建AVStream 视频流

//原型
向媒体文件添加一个新流。
s media file handle,c可以传入特殊指定 否则默认AVFormatContext里面的
AVStream *avformat_new_stream(AVFormatContext *s, const AVCodec *c);
//使用
video_st = avformat_new_stream(pFormatCtx, 0);

第4步、给AVCodecContext解码器上下文属性赋值,并创建打开解码器

AVCodecContext* pCodecCtx;
AVCodec* pCodec;
	
pCodecCtx = video_st->codec;
//pCodecCtx->codec_id =AV_CODEC_ID_HEVC;
pCodecCtx->codec_id = fmt->video_codec;
pCodecCtx->codec_type = AVMEDIA_TYPE_VIDEO;
pCodecCtx->pix_fmt = AV_PIX_FMT_YUV420P;
pCodecCtx->width = in_w;
pCodecCtx->height = in_h;
pCodecCtx->bit_rate = 400000;
pCodecCtx->gop_size = 250;
pCodecCtx->time_base.num = 1;
pCodecCtx->time_base.den = 25;
//查找具有匹配编解码器ID的已注册编码器。
pCodec = avcodec_find_encoder(pCodecCtx->codec_id);
if (!pCodec) {
	printf("Can not find encoder! \n");
	return -1;
}
if (avcodec_open2(pCodecCtx, pCodec, &param) < 0) {
	printf("Failed to open encoder! \n");
	return -1;
}

第5步、给读取的帧申请缓存,布置data大小

//存储一帧像素数据缓冲区
pFrame = av_frame_alloc();
picture_size = av_image_get_buffer_size(pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height, 1);
pFrame_buf = (uint8_t *)av_malloc(picture_size);
av_image_fill_arrays(pFrame->data, pFrame->linesize, pFrame_buf,AV_PIX_FMT_YUV420P, pCodecCtx->width, pCodecCtx->height, 1);
pFrame->width = pCodecCtx->width;
pFrame->height = pCodecCtx->height;
pFrame->format = pCodecCtx->pix_fmt;

第6步、读取写入了

//分配流私有数据并将流头写入输出媒体文件。
avformat_write_header(pFormatCtx, NULL);
for (int i = 0; i<framenum; i++) 
{
	//从文件中读取YUV数据
	if (fread(picture_buf, 1, y_size * 3 / 2, in_file) <= 0) {
		printf("Failed to read raw data! \n");
		getchar();
		return -1;
	}
	else if (feof(in_file)) {
		break;
	}
	//给AVFrame赋值
	pFrame->data[0] = picture_buf;              // Y
	pFrame->data[1] = picture_buf + y_size;      // U 
	pFrame->data[2] = picture_buf + y_size * 5 / 4;  // V  y_size+y_size/4个位置的U
	pFrame->pts = i*(video_st->time_base.den) / ((video_st->time_base.num) * 25);
	int got_picture = 0;
	//成功 解码
	int ret = avcodec_encode_video2(pCodecCtx, pkt, pFrame, &got_picture);
	if (ret < 0) {
		printf("Failed to encode! \n");
		return -1;
	}
	if (got_picture == 1) {
		printf("Succeed to encode frame: %5d\tsize:%5d\n", framecnt, pkt->size);
		framecnt++;
		pkt->stream_index = video_st->index;
		//写入到文件
		ret = av_write_frame(pFormatCtx, pkt);
		av_free_packet(pkt);
	}
}
//最后还要将缓冲中的写入
//Flush Encoder
ret = flush_encoder(pFormatCtx, 0);
if (ret < 0) {
	printf("Flushing encoder failed\n");
	getchar();
	return -1;
}

//Write file trailer
av_write_trailer(pFormatCtx);

//将avcodec_encode_video2替换成新的API不知道为什么总是失败,avcodec_receive_packet的时候总是提示EAGAIN错误,
/*  失败 avcodec_receive_packet总是返回EAGAIN导致没有包出来
//Encode
ret = avcodec_send_frame(pCodecCtx, pFrame);
if (ret < 0) {
	printf("Failed to encode! \n");
	getchar();
	return -1;
}
while (ret >= 0) {
	ret = avcodec_receive_packet(pCodecCtx, pkt);
	if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
	{
		av_free_packet(pkt);
		break;
	}
	else if (ret < 0) {
		fprintf(stderr, "Error during encoding\n");
		exit(1);
	}
	if (ret == 1) {
		printf("Succeed to encode frame: %5d\tsize:%5d\n", framecnt, pkt->size);
		framecnt++;
		pkt->stream_index = video_st->index;
		ret = av_write_frame(pFormatCtx, pkt);
		av_free_packet(pkt);
	}
}
*/

实践代码


int flush_encoder(AVFormatContext *fmt_ctx, unsigned int stream_index) {
	int ret;
	int got_frame;
	AVPacket enc_pkt;
	if (!(fmt_ctx->streams[stream_index]->codec->codec->capabilities &
		CODEC_CAP_DELAY))
		return 0;
	while (1) {
		enc_pkt.data = NULL;
		enc_pkt.size = 0;
		av_init_packet(&enc_pkt);
		ret = avcodec_encode_video2(fmt_ctx->streams[stream_index]->codec, &enc_pkt,
			NULL, &got_frame);
		av_frame_free(NULL);
		if (ret < 0)
			break;
		if (!got_frame) {
			ret = 0;
			break;
		}
		printf("Flush Encoder: Succeed to encode 1 frame!\tsize:%5d\n", enc_pkt.size);
		/* mux encoded frame */
		ret = av_write_frame(fmt_ctx, &enc_pkt);
		if (ret < 0)
			break;
	}
	return ret;
}

int main(int argc, char* argv[])
{
	AVFormatContext* pFormatCtx;
	AVOutputFormat* fmt;
	AVStream* video_st;
	AVCodecContext* pCodecCtx;
	AVCodec* pCodec;
	AVPacket* pkt;
	uint8_t* picture_buf;
	uint8_t*pFrame_buf;
	AVFrame* pFrame;
	int picture_size;
	int y_size;
	int framecnt = 0;
	int ret;
	//FILE *in_file = fopen("src01_480x272.yuv", "rb");	//Input raw YUV data 
	FILE *in_file = fopen("output240X128.yuv", "rb");   //Input raw YUV data
	int in_w = 240, in_h = 128;                              //Input data's width and height
	int framenum = 100;                                   //Frames to encode
														  //const char* out_file = "src01.h264";              //Output Filepath 
														  //const char* out_file = "src01.ts";
														  //const char* out_file = "src01.hevc";
	const char* out_file = "ds.h264";

	av_register_all();
	/*
	//Method1.
	pFormatCtx = avformat_alloc_context();
	//av_guess_format在注册输出格式列表中返回与所提供的参数最匹配的输出格式,如果没有匹配则返回NULL。
	fmt = av_guess_format(NULL, out_file, NULL);//根据文件名去匹配输出格式AVOutputFormat
	pFormatCtx->oformat = fmt;
	*/
	
	//Method 2.
	//为输出格式分配一个AVFormatContext。
	//int avformat_alloc_output_context2(AVFormatContext **ctx, AVOutputFormat *oformat,const char *format_name, const char *filename);
	//oformat用于分配上下文的格式,如果为NULL则用format_name、filename代替
	//format_name用于分配上下文的输出格式的名称,如果为NULL则使用filename文件名代替
	//filename用于分配上下文的文件名
	avformat_alloc_output_context2(&pFormatCtx, NULL, NULL, out_file);
	fmt = pFormatCtx->oformat;
	

	//Open output URL
	//创建并初始化一个AVIOContext,用于访问url指示的资源。
	if (avio_open(&pFormatCtx->pb, out_file, AVIO_FLAG_READ_WRITE) < 0) {
		printf("Failed to open output file! \n");
		return -1;
	}

	video_st = avformat_new_stream(pFormatCtx, 0);
	//video_st->time_base.num = 1; 
	//video_st->time_base.den = 25;  

	if (video_st == NULL) {
		return -1;
	}
	//Param that must set
	pCodecCtx = video_st->codec;
	//pCodecCtx->codec_id =AV_CODEC_ID_HEVC;
	pCodecCtx->codec_id = fmt->video_codec;
	pCodecCtx->codec_type = AVMEDIA_TYPE_VIDEO;
	pCodecCtx->pix_fmt = AV_PIX_FMT_YUV420P;
	pCodecCtx->width = in_w;
	pCodecCtx->height = in_h;
	pCodecCtx->bit_rate = 400000;
	pCodecCtx->gop_size = 250;

	pCodecCtx->time_base.num = 1;
	pCodecCtx->time_base.den = 25;

	//H264
	//pCodecCtx->me_range = 16;
	//pCodecCtx->max_qdiff = 4;
	//pCodecCtx->qcompress = 0.6;
	pCodecCtx->qmin = 10;
	pCodecCtx->qmax = 51;

	//Optional Param
	pCodecCtx->max_b_frames = 3;

	// Set Option
	AVDictionary *param = 0;
	//H.264
	if (pCodecCtx->codec_id == AV_CODEC_ID_H264) {
		av_dict_set(&param, "preset", "slow", 0);
		av_dict_set(&param, "tune", "zerolatency", 0);
		//av_dict_set(param, "profile", "main", 0);
	}
	//H.265
	if (pCodecCtx->codec_id == AV_CODEC_ID_H265) {
		av_dict_set(&param, "preset", "ultrafast", 0);
		av_dict_set(&param, "tune", "zero-latency", 0);
	}

	//Show some Information
	av_dump_format(pFormatCtx, 0, out_file, 1);

	//查找具有匹配编解码器ID的已注册编码器。
	pCodec = avcodec_find_encoder(pCodecCtx->codec_id);
	if (!pCodec) {
		printf("Can not find encoder! \n");
		return -1;
	}
	if (avcodec_open2(pCodecCtx, pCodec, &param) < 0) {
		printf("Failed to open encoder! \n");
		return -1;
	}


	//存储一帧像素数据缓冲区
	pFrame = av_frame_alloc();
	picture_size = av_image_get_buffer_size(pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height, 1);
	picture_buf = (uint8_t *)av_malloc(picture_size);
	pFrame_buf = (uint8_t *)av_malloc(picture_size);
	//av_image_fill_arrays((AVPicture *)pFrame, picture_buf, pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height);//淘汰了
	av_image_fill_arrays(pFrame->data, pFrame->linesize, pFrame_buf,AV_PIX_FMT_YUV420P, pCodecCtx->width, pCodecCtx->height, 1);
	pFrame->width = pCodecCtx->width;
	pFrame->height = pCodecCtx->height;
	pFrame->format = pCodecCtx->pix_fmt;
	/*ret = av_frame_get_buffer(pFrame, picture_size);
	if (ret < 0) {
		fprintf(stderr, "Could not allocate the video frame data\n");
		exit(1);
	}*/
	//Write File Header
	avformat_write_header(pFormatCtx, NULL);
	pkt = av_packet_alloc();
	//av_new_packet(&pkt, picture_size);

	y_size = pCodecCtx->width * pCodecCtx->height;
	
	for (int i = 0; i<framenum; i++) 
	{
		fflush(stdout);
		/*ret = av_frame_make_writable(pFrame);
		if (ret < 0) {
			printf("Failed to av_frame_make_writable! \n");
			getchar();
			return -1;
		}*/
		//Read raw YUV data   一个像素YUV420  4 1 1   4个像素6个字节表示,一个像素1.5个字节
		if (fread(picture_buf, 1, y_size * 3 / 2, in_file) <= 0) {
			printf("Failed to read raw data! \n");
			getchar();
			return -1;
		}
		else if (feof(in_file)) {
			break;
		}
		pFrame->data[0] = picture_buf;              // Y
		pFrame->data[1] = picture_buf + y_size;      // U 
		pFrame->data[2] = picture_buf + y_size * 5 / 4;  // V  y_size+y_size/4个位置的U
		pFrame->pts = i*(video_st->time_base.den) / ((video_st->time_base.num) * 25);
		int got_picture = 0;
		//成功
		//Encode
		int ret = avcodec_encode_video2(pCodecCtx, pkt, pFrame, &got_picture);
		if (ret < 0) {
			printf("Failed to encode! \n");
			return -1;
		}
		if (got_picture == 1) {
			printf("Succeed to encode frame: %5d\tsize:%5d\n", framecnt, pkt->size);
			framecnt++;
			pkt->stream_index = video_st->index;
			ret = av_write_frame(pFormatCtx, pkt);
			av_free_packet(pkt);
		}
		/*  失败 avcodec_receive_packet总是返回EAGAIN导致没有包出来
		//Encode
		ret = avcodec_send_frame(pCodecCtx, pFrame);
		if (ret < 0) {
			printf("Failed to encode! \n");
			getchar();
			return -1;
		}
		while (ret >= 0) {
			ret = avcodec_receive_packet(pCodecCtx, pkt);
			if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
			{
				av_free_packet(pkt);
				break;
			}
			else if (ret < 0) {
				fprintf(stderr, "Error during encoding\n");
				exit(1);
			}
			if (ret == 1) {
				printf("Succeed to encode frame: %5d\tsize:%5d\n", framecnt, pkt->size);
				framecnt++;
				pkt->stream_index = video_st->index;
				ret = av_write_frame(pFormatCtx, pkt);
				av_free_packet(pkt);
			}
		}
		*/
	}
	//Flush Encoder
	ret = flush_encoder(pFormatCtx, 0);
	if (ret < 0) {
		printf("Flushing encoder failed\n");
		getchar();
		return -1;
	}

	//Write file trailer
	av_write_trailer(pFormatCtx);

	//Clean
	if (video_st) {
		avcodec_close(video_st->codec);
		av_free(pFrame);
		av_free(picture_buf);
	}
	avio_close(pFormatCtx->pb);
	avformat_free_context(pFormatCtx);

	//fclose(in_file);

	getchar();

	return 0;
}

ffmpeg-4.0.2\doc\examples\encode_video.c代码


#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <libavcodec/avcodec.h>

#include <libavutil/opt.h>
#include <libavutil/imgutils.h>

static void encode(AVCodecContext *enc_ctx, AVFrame *frame, AVPacket *pkt,
                   FILE *outfile)
{
    int ret;

    /* send the frame to the encoder */
    if (frame)
        printf("Send frame %3"PRId64"\n", frame->pts);

    ret = avcodec_send_frame(enc_ctx, frame);
    if (ret < 0) {
        fprintf(stderr, "Error sending a frame for encoding\n");
        exit(1);
    }

    while (ret >= 0) {
        ret = avcodec_receive_packet(enc_ctx, pkt);
        if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
            return;
        else if (ret < 0) {
            fprintf(stderr, "Error during encoding\n");
            exit(1);
        }

        printf("Write packet %3"PRId64" (size=%5d)\n", pkt->pts, pkt->size);
        fwrite(pkt->data, 1, pkt->size, outfile);
        av_packet_unref(pkt);
    }
}

int main(int argc, char **argv)
{
    const char *filename, *codec_name;
    const AVCodec *codec;
    AVCodecContext *c= NULL;
    int i, ret, x, y;
    FILE *f;
    AVFrame *frame;
    AVPacket *pkt;
    uint8_t endcode[] = { 0, 0, 1, 0xb7 };

    if (argc <= 2) {
        fprintf(stderr, "Usage: %s <output file> <codec name>\n", argv[0]);
        exit(0);
    }
    filename = argv[1];
    codec_name = argv[2];

    /* find the mpeg1video encoder */
    codec = avcodec_find_encoder_by_name(codec_name);
    if (!codec) {
        fprintf(stderr, "Codec '%s' not found\n", codec_name);
        exit(1);
    }

    c = avcodec_alloc_context3(codec);
    if (!c) {
        fprintf(stderr, "Could not allocate video codec context\n");
        exit(1);
    }

    pkt = av_packet_alloc();
    if (!pkt)
        exit(1);

    /* put sample parameters */
    c->bit_rate = 400000;
    /* resolution must be a multiple of two */
    c->width = 352;
    c->height = 288;
    /* frames per second */
    c->time_base = (AVRational){1, 25};
    c->framerate = (AVRational){25, 1};

    /* emit one intra frame every ten frames
     * check frame pict_type before passing frame
     * to encoder, if frame->pict_type is AV_PICTURE_TYPE_I
     * then gop_size is ignored and the output of encoder
     * will always be I frame irrespective to gop_size
     */
    c->gop_size = 10;
    c->max_b_frames = 1;
    c->pix_fmt = AV_PIX_FMT_YUV420P;

    if (codec->id == AV_CODEC_ID_H264)
        av_opt_set(c->priv_data, "preset", "slow", 0);

    /* open it */
    ret = avcodec_open2(c, codec, NULL);
    if (ret < 0) {
        fprintf(stderr, "Could not open codec: %s\n", av_err2str(ret));
        exit(1);
    }

    f = fopen(filename, "wb");
    if (!f) {
        fprintf(stderr, "Could not open %s\n", filename);
        exit(1);
    }

    frame = av_frame_alloc();
    if (!frame) {
        fprintf(stderr, "Could not allocate video frame\n");
        exit(1);
    }
    frame->format = c->pix_fmt;
    frame->width  = c->width;
    frame->height = c->height;

    ret = av_frame_get_buffer(frame, 32);
    if (ret < 0) {
        fprintf(stderr, "Could not allocate the video frame data\n");
        exit(1);
    }

    /* encode 1 second of video */
    for (i = 0; i < 25; i++) {
        fflush(stdout);

        /* make sure the frame data is writable */
        ret = av_frame_make_writable(frame);
        if (ret < 0)
            exit(1);

        /* prepare a dummy image */
        /* Y */
        for (y = 0; y < c->height; y++) {
            for (x = 0; x < c->width; x++) {
                frame->data[0][y * frame->linesize[0] + x] = x + y + i * 3;
            }
        }

        /* Cb and Cr */
        for (y = 0; y < c->height/2; y++) {
            for (x = 0; x < c->width/2; x++) {
                frame->data[1][y * frame->linesize[1] + x] = 128 + y + i * 2;
                frame->data[2][y * frame->linesize[2] + x] = 64 + x + i * 5;
            }
        }

        frame->pts = i;

        /* encode the image */
        encode(c, frame, pkt, f);
    }

    /* flush the encoder */
    encode(c, NULL, pkt, f);

    /* add sequence end code to have a real MPEG file */
    fwrite(endcode, 1, sizeof(endcode), f);
    fclose(f);

    avcodec_free_context(&c);
    av_frame_free(&frame);
    av_packet_free(&pkt);

    return 0;
}

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