avcodec_flush_buffers

avcodec_flush_buffers是FFmpeg库中的一个函数，用于刷新解码器的缓冲区。它的原型如下：
void avcodec_flush_buffers(AVCodecContext *avctx);
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参数说明：

avctx：指向AVCodecContext结构体的指针，表示要刷新缓冲区的解码器上下文。

该函数的作用是将解码器的缓冲区进行清空，以便重新开始解码新的数据。在某些情况下，可能需要清空缓冲区，例如切换到新的视频流或重新定位到视频文件的特定位置时。
请注意，avcodec_flush_buffers函数只清空解码器的缓冲区，不会关闭解码器或释放其他资源。如果需要关闭解码器，可以使用avcodec_close函数。
这只是对avcodec_flush_buffers函数的简要说明，如果需要更详细的信息，可以参考FFmpeg的官方文档或相关资料。

相关问题

c/c++使用ffmpeg库推流本地文件，并使用av_seek_frame实现跳转功能

要使用FFmpeg库进行推流和跳转功能，需要按照以下步骤进行操作：

初始化FFmpeg库

在使用FFmpeg库之前，需要先初始化FFmpeg库。可以使用av_register_all()函数进行初始化。
av_register_all();
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打开输入文件

使用avformat_open_input()函数打开输入文件，然后使用avformat_find_stream_info()函数查找文件中的流信息。
AVFormatContext *formatCtx = NULL;
avformat_open_input(&formatCtx, inputFile, NULL, NULL);
avformat_find_stream_info(formatCtx, NULL);
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打开输出文件

使用avformat_alloc_output_context2()函数创建输出文件的AVFormatContext，并使用avio_open()函数打开输出文件。
AVFormatContext *outFormatCtx = NULL;
avformat_alloc_output_context2(&outFormatCtx, NULL, NULL, outputFile);
AVIOContext *outAVIOContext = NULL;
avio_open(&outAVIOContext, outputFile, AVIO_FLAG_WRITE);
outFormatCtx->pb = outAVIOContext;
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为输出文件添加流

使用avformat_new_stream()函数为输出文件添加音频或视频流，并设置流的编码格式和参数。
AVStream *outStream = avformat_new_stream(outFormatCtx, NULL);
outStream->codecpar->codec_id = codecId;
outStream->codecpar->codec_type = codecType;
outStream->codecpar->width = width;
outStream->codecpar->height = height;
outStream->codecpar->sample_rate = sampleRate;
outStream->codecpar->channels = channels;
outStream->codecpar->format = AV_SAMPLE_FMT_FLTP;
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打开编码器

使用avcodec_find_encoder()函数查找流的编码器，并使用avcodec_open2()函数打开编码器。
AVCodec *encoder = avcodec_find_encoder(outStream->codecpar->codec_id);
AVCodecContext *encoderCtx = avcodec_alloc_context3(encoder);
avcodec_parameters_to_context(encoderCtx, outStream->codecpar);
avcodec_open2(encoderCtx, encoder, NULL);
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写入文件头

使用avformat_write_header()函数写入输出文件的文件头。
avformat_write_header(outFormatCtx, NULL);
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读取和写入数据

使用av_read_frame()函数读取输入文件中的数据，并使用av_write_frame()函数将数据写入输出文件。如果需要跳转到指定时间点，可以使用av_seek_frame()函数进行跳转。
while (av_read_frame(formatCtx, &packet) == 0) {
if (packet.stream_index == streamIndex) {
if (av_seek_frame(formatCtx, streamIndex, timestamp, AVSEEK_FLAG_BACKWARD) >= 0) {
avcodec_flush_buffers(decoderCtx);
continue;
}
avcodec_send_packet(decoderCtx, &packet);
while (avcodec_receive_frame(decoderCtx, frame) == 0) {
// 对音视频数据进行处理
avcodec_send_frame(encoderCtx, frame);
while (avcodec_receive_packet(encoderCtx, &outPacket) == 0) {
outPacket.stream_index = outStream->index;
av_interleaved_write_frame(outFormatCtx, &outPacket);
av_packet_unref(&outPacket);
}
}
}
av_packet_unref(&packet);
}
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关闭和释放资源

使用av_write_trailer()函数写入输出文件的文件尾，并使用avformat_close_input()、avformat_close_output()等函数关闭输入输出文件，并释放相应的资源。
av_write_trailer(outFormatCtx);
avformat_close_input(&formatCtx);
avformat_close_input(&outFormatCtx);
avcodec_close(decoderCtx);
avcodec_close(encoderCtx);
avformat_free_context(formatCtx);
avformat_free_context(outFormatCtx);
av_frame_free(&frame);
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c/c++使用ffmpeg库推流本地文件，并使用av_seek_frame实现跳转功能的完整代码

这里是使用ffmpeg库推流本地文件，并使用av_seek_frame实现跳转功能的完整C++代码：
#include <iostream>
#include <string>

extern "C" {
#include <libavformat/avformat.h>
#include <libavutil/mathematics.h>
}

#define STREAM_DURATION 10.0
#define STREAM_FRAME_RATE 25 /* 25 images/s */
#define STREAM_PIX_FMT AV_PIX_FMT_YUV420P /* default pix_fmt */

/* add a video output stream */
static AVStream *add_video_stream(AVFormatContext *oc, enum AVCodecID codec_id) {
AVCodecContext *c;
AVStream *st;

st = avformat_new_stream(oc, NULL);
if (!st) {
std::cerr << "Could not allocate stream" << std::endl;
exit(1);
}

c = st->codec;
c->codec_id = codec_id;
c->codec_type = AVMEDIA_TYPE_VIDEO;

/* 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, STREAM_FRAME_RATE };
st->time_base = c->time_base;

c->gop_size = 12; /* emit one intra frame every twelve frames at most */
c->pix_fmt = STREAM_PIX_FMT;

/* some formats want stream headers to be separate */
if (oc->oformat->flags &amp; AVFMT_GLOBALHEADER)
c->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;

return st;
}

/* open the output file, and allocate the format context */
static void open_output_file(const std::string &amp;filename, AVFormatContext **oc, AVOutputFormat *fmt) {
int ret;

/* allocate the output media context */
avformat_alloc_output_context2(oc, fmt, NULL, filename.c_str());
if (!(*oc)) {
std::cerr << "Could not create output context" << std::endl;
exit(1);
}

/* add the video stream using the default format codecs and initialize the codecs */
add_video_stream(*oc, (*oc)->oformat->video_codec);

/* open the output file, if needed */
if (!((*oc)->oformat->flags &amp; AVFMT_NOFILE)) {
ret = avio_open(&amp;(*oc)->pb, filename.c_str(), AVIO_FLAG_WRITE);
if (ret < 0) {
std::cerr << "Could not open output file" << std::endl;
exit(1);
}
}

/* write the stream header, if any */
ret = avformat_write_header(*oc, NULL);
if (ret < 0) {
std::cerr << "Error occurred when opening output file" << std::endl;
exit(1);
}
}

/* close the output file and free the format context */
static void close_output_file(AVFormatContext *oc) {
/* write the trailer, if any */
av_write_trailer(oc);

/* close the output file */
if (!(oc->oformat->flags &amp; AVFMT_NOFILE))
avio_closep(&amp;oc->pb);

/* free the stream */
avformat_free_context(oc);
}

/* seek to a specific frame in a video file */
static void seek_to_frame(AVFormatContext *fmt_ctx, int stream_index, int64_t timestamp) {
int ret;

/* seek to the timestamp */
ret = av_seek_frame(fmt_ctx, stream_index, timestamp, AVSEEK_FLAG_BACKWARD);
if (ret < 0) {
std::cerr << "Error seeking to timestamp " << timestamp << std::endl;
exit(1);
}

/* flush the codec buffers */
avcodec_flush_buffers(fmt_ctx->streams[stream_index]->codec);
}

int main(int argc, char **argv) {
if (argc != 2) {
std::cerr << "Usage: " << argv[0] << " <output file>" << std::endl;
return 1;
}

AVOutputFormat *fmt;
AVFormatContext *oc;
AVPacket pkt;
int frame_count, i;
double t, tincr;
int64_t next_pts;

/* register all codecs and formats */
av_register_all();

/* allocate the output media context */
fmt = av_guess_format(NULL, argv[1], NULL);
if (!fmt) {
std::cerr << "Could not determine output format" << std::endl;
return 1;
}
open_output_file(argv[1], &amp;oc, fmt);

/* initialize the frame counter */
frame_count = 0;

/* initialize the timestamp increment */
tincr = 2 * M_PI * STREAM_FRAME_RATE / STREAM_DURATION;
next_pts = 0;

/* main loop */
for (i = 0; i < 100; i++) {
AVStream *st;
AVCodecContext *c;
AVRational time_base;
AVFrame *frame;
int got_packet = 0;
int ret;

/* get the video stream */
st = oc->streams[0];
c = st->codec;
time_base = st->time_base;

/* allocate a new frame */
frame = av_frame_alloc();
if (!frame) {
std::cerr << "Could not allocate video frame" << std::endl;
exit(1);
}

/* generate synthetic video */
frame->pts = av_rescale_q(frame_count, time_base, c->time_base);
frame->format = c->pix_fmt;
frame->width = c->width;
frame->height = c->height;
ret = av_frame_get_buffer(frame, 0);
if (ret < 0) {
std::cerr << "Could not allocate frame data" << std::endl;
exit(1);
}
for (int y = 0; y < c->height; y++)
for (int x = 0; x < c->width; x++)
frame->data[0][y * frame->linesize[0] + x] = x + y + frame_count * 3;
for (int y = 0; y < c->height / 2; y++) {
for (int x = 0; x < c->width / 2; x++) {
frame->data[1][y * frame->linesize[1] + x] = 128 + y + frame_count * 2;
frame->data[2][y * frame->linesize[2] + x] = 64 + x + frame_count * 5;
}
}

/* encode the frame */
av_init_packet(&amp;pkt);
pkt.data = NULL;
pkt.size = 0;
ret = avcodec_encode_video2(c, &amp;pkt, frame, &amp;got_packet);
if (ret < 0) {
std::cerr << "Error encoding video frame" << std::endl;
exit(1);
}

/* if the frame was encoded, write it to the file */
if (got_packet) {
pkt.stream_index = st->index;
av_packet_rescale_ts(&amp;pkt, time_base, st->time_base);
ret = av_interleaved_write_frame(oc, &amp;pkt);
if (ret < 0) {
std::cerr << "Error while writing video frame" << std::endl;
exit(1);
}
}

/* increase the frame count */
frame_count++;

/* calculate the next presentation timestamp */
t = (double)frame_count / STREAM_FRAME_RATE;
next_pts += (int64_t)(tincr * 1000);
if (next_pts > (double)av_gettime()) {
av_usleep(next_pts - av_gettime());
}

/* free the frame */
av_frame_free(&amp;frame);
}

/* seek to a specific frame */
seek_to_frame(oc, 0, 30);

/* continue encoding frames */
for (; i < 200; i++) {
AVStream *st;
AVCodecContext *c;
AVRational time_base;
AVFrame *frame;
int got_packet = 0;
int ret;

/* get the video stream */
st = oc->streams[0];
c = st->codec;
time_base = st->time_base;

/* allocate a new frame */
frame = av_frame_alloc();
if (!frame) {
std::cerr << "Could not allocate video frame" << std::endl;
exit(1);
}

/* generate synthetic video */
frame->pts = av_rescale_q(frame_count, time_base, c->time_base);
frame->format = c->pix_fmt;
frame->width = c->width;
frame->height = c->height;
ret = av_frame_get_buffer(frame, 0);
if (ret < 0) {
std::cerr << "Could not allocate frame data" << std::endl;
exit(1);
}
for (int y = 0; y < c->height; y++)
for (int x = 0; x < c->width; x++)
frame->data[0][y * frame->linesize[0] + x] = x + y + frame_count * 3;
for (int y = 0; y < c->height / 2; y++) {
for (int x = 0; x < c->width / 2; x++) {
frame->data[1][y * frame->linesize[1] + x] = 128 + y + frame_count * 2;
frame->data[2][y * frame->linesize[2] + x] = 64 + x + frame_count * 5;
}
}

/* encode the frame */
av_init_packet(&amp;pkt);
pkt.data = NULL;
pkt.size = 0;
ret = avcodec_encode_video2(c, &amp;pkt, frame, &amp;got_packet);
if (ret < 0) {
std::cerr << "Error encoding video frame" << std::endl;
exit(1);
}

/* if the frame was encoded, write it to the file */
if (got_packet) {
pkt.stream_index = st->index;
av_packet_rescale_ts(&amp;pkt, time_base, st->time_base);
ret = av_interleaved_write_frame(oc, &amp;pkt);
if (ret < 0) {
std::cerr << "Error while writing video frame" << std::endl;
exit(1);
}
}

/* increase the frame count */
frame_count++;

/* calculate the next presentation timestamp */
t = (double)frame_count / STREAM_FRAME_RATE;
next_pts += (int64_t)(tincr * 1000);
if (next_pts > (double)av_gettime()) {
av_usleep(next_pts - av_gettime());
}

/* free the frame */
av_frame_free(&amp;frame);
}

/* close the output file and free the format context */
close_output_file(oc);

return 0;
}
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这个代码会生成一个10秒的视频，并在第30帧处进行跳转，继续生成另外10秒的视频。视频中的图像是随机生成的。你可以根据自己的需求进行修改。