标签：过程 err reads 它的 lock context ble 情况下 打开
最近有工作需求用到ffmpeg，分享下。包括一些编码的基础知识，ffmpeg视频解码基础，还有GPU解码的部分。
属于科普工作，并不深入，记录了踩过的一些坑，希望有用
饮水思源：雷霄骅（雷神） &
代码部分参考自 同事***（打码）代码，谢谢大神！
FFmpeg是一种功能强大的常用的视频/音频处理开源框架。支持几乎所有主流格式音视频的编解码，并能进行拼接等操作。
封装格式和编码格式的关系：封装格式可以理解为存放编码后音视频信息的一种容器，不通的容器对支持的编码格式有所不同。
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整体解码流程：
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h264 h264参考博客:
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由于人类对与色彩的感知能力有限，所以通常会选择降低颜色信息密度，即对UV分量进行压缩
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基于YUV分量在存储方式上的不同，又衍生出YUV420SP,YUV420P等格式
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struct buffer_data {
uint8_t *ptr_;
size_t size_;
};
typedef buffer_data BufferData;
int VideoParseFFmpeg::read_packet(void *opaque, uint8_t *buf, int buf_size) {
//opaque用户自定义指针
struct buffer_data *bd = (struct buffer_data *) opaque;
buf_size = FFMIN(buf_size, bd->size_);
if (!buf_size)
return AVERROR_EOF;
memcpy(buf, bd->ptr_, buf_size);
bd->ptr_ += buf_size;
bd->size_ -= buf_size;
return buf_size;
}
int LoadContent(const std::string &video_content){
int ret = 0;
//分配缓存空间
video_size_ = video_content.size();
avio_ctx_buffer_size_ = video_size_+AV_INPUT_BUFFER_PADDING_SIZE;
avio_ctx_buffer_ = (uint8_t *)av_malloc(avio_ctx_buffer_size_);
//bd为自定义结构，指向内存中的视频文件
bd_.ptr_ = (uint8_t *)video_content.c_str();
bd_.size_ = video_content.size();
input_ctx_ = avformat_alloc_context();
//自定义io
avio_ctx_ = avio_alloc_context(avio_ctx_buffer_,
avio_ctx_buffer_size_,
0,
&bd_,
&read_packet, //自定义读取回调
NULL,
NULL);
AVInputFormat *in_fmt{NULL};
//视频格式探测
if((ret = av_probe_input_buffer(avio_ctx_, &in_fmt_, "", NULL, 0, 0)) < 0) {
LOGGER_WARN(Log::GetLog(), "fail to prob input, err [{}]", AVERROR(ret));
return -1;
}
//注册iocontext
input_ctx_->pb = avio_ctx_;
/* open the input file */
if ((ret = avformat_open_input(&input_ctx_, "", in_fmt_, NULL)) != 0) {
LOGGER_WARN(Log::GetLog(), "fail to open input, err [{}]", AVERROR(ret));
return -1;
}
// if ((ret = avformat_open_input(&input_ctx_, "./smoke.mp4", NULL, NULL)) != 0) {
// LOGGER_WARN(Log::GetLog(), "fail to open input, err [{}]", AVERROR(ret));
// return -1;
// }
//获取流信息
if ((ret = avformat_find_stream_info(input_ctx_, NULL)) < 0) {
LOGGER_WARN(Log::GetLog(), "fail to find input stream information, err[{}]", AVERROR(ret));
return -1;
}
/* find the video stream information */
//找到视频流，获取其对应的decoder
if ((ret = av_find_best_stream(input_ctx_, AVMEDIA_TYPE_VIDEO, -1, -1, &decoder_, 0)) < 0) {
LOGGER_WARN(Log::GetLog(), "fail to find a video stream from input, err[{}]", ret);
return -1;
}
video_stream_idx_ = ret;
//获取decoder_context，把decoder注册进去
if (!(decoder_ctx_ = avcodec_alloc_context3(decoder_))) {
LOGGER_WARN(Log::GetLog(), "fail to alloc avcodec context");
return -1;
}
video_stream_ = input_ctx_->streams[video_stream_idx_];
//新版本不再将音视频流信息直接保存到streams[video_stream_idx_]中，而是存放在AVCodecParammeters中（涉及format，width，height，codec_type等），该函数提供了转换
if ((ret = avcodec_parameters_to_context(decoder_ctx_, video_stream_->codecpar)) < 0){
LOGGER_WARN(Log::GetLog(), "fail to convert parameters to context, err [{}]", ret);
return -1;
}
//获取帧率等基本信息
if(video_stream_->avg_frame_rate.den != 0) {
fps_ = video_stream_->avg_frame_rate.num / video_stream_->avg_frame_rate.den;
}
video_length_sec_ = input_ctx_->duration/AV_TIME_BASE;
//YUV420p等
pix_fmt_ = (AVPixelFormat)video_stream_->codecpar->format;
//硬解码部分
if (hw_enable_ && is_hw_support_fmt(pix_fmt_)) {
for (int i = 0;; i++)
{
const AVCodecHWConfig *config = avcodec_get_hw_config(decoder_, i);
if (!config) {
LOGGER_WARN(Log::GetLog(), "decoder [{}] does not support device type [{}]", decoder_->name, av_hwdevice_get_type_name(hw_type_));
return -1;
}
if (config->methods & AV_CODEC_HW_CONFIG_METHOD_HW_DEVICE_CTX &&
config->device_type == hw_type_) {
hw_pix_fmt_ = config->pix_fmt;
break;
}
}
decoder_ctx_->pix_fmt = hw_pix_fmt_;
if ((ret = hw_decoder_init(decoder_ctx_, hw_type_)) < 0) {
LOGGER_WARN(Log::GetLog(), "fail to init hw decoder, err [{}]", ret);
return -1;
}
}
if ((ret = avcodec_open2(decoder_ctx_, decoder_, NULL)) < 0) {
LOGGER_WARN(Log::GetLog(), "fail to open decodec, err[{}]", ret);
return -1;
}
} while (true) {
if ((av_read_frame(input_ctx_, &packet_)) < 0){
break;
}
if (video_stream_idx_ == packet_.stream_index) {
//std::shared_ptr<cv::Mat> p_frame = nullptr;
decode_write(decoder_ctx_, &packet_, &buffer, frames);
//frames.push_back(p_frame);
}
}
/* flush the decoder */
packet_.data = NULL;
packet_.size = 0;
//std::shared_ptr<cv::Mat> p_frame = nullptr;
//cv::Mat *p_frame = NULL;
decode_write(decoder_ctx_, &packet_, &buffer, frames);
====================================================
//code block in decode_write
ret = avcodec_send_packet(avctx, packet);
if (ret < 0) {
LOGGER_WARN(Log::GetLog(), "error during decodeing, err[{}]", AVERROR(ret));
return ret;
}
while (true)
{
auto clear = [&frame, &sw_frame, this]{
if (frame != NULL)
av_frame_free(&frame);
if (sw_frame != NULL)
av_frame_free(&sw_frame);
av_packet_unref(&packet_);
};
if (!(frame = av_frame_alloc()) || !(sw_frame = av_frame_alloc()))
{
LOGGER_WARN(Log::GetLog(), "cant alloc frame, err[{}]", AVERROR(ENOMEM));
clear();
return 0;
}
ret = avcodec_receive_frame(avctx, frame);
if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
clear();
return 0;
}
else if (ret < 0) {
LOGGER_WARN(Log::GetLog(), "error while decoding, err[{}]", AVERROR(ret));
clear();
return ret;
}
...
}./configure --prefix=./ --bindir=bin/ffmpeg --incdir=include/ffmpeg --libdir=lib64/ffmpeg --disable-x86asm --arch=x86_64 --optflags='-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches -m64 -mtune=generic' --extra-ldflags='-Wl,-z,relro' --enable-libx264 --enable-libx265 --enable-avfilter --enable-pthreads --enable-shared --enable-gpl --disable-debug --enable-cuda --enable-cuvid --enable-nvenc --enable-nonfree --enable-libnpp --extra-cflags=-I/usr/local/cuda-8.0/include --extra-ldflags=-L/usr/local/cuda-8.0/lib64//配置解码器
if (hw_enable_ && is_hw_support_fmt(pix_fmt_)) {
for (int i = 0;; i++)
{
//获取支持该decoder的hw 配置型
const AVCodecHWConfig *config = avcodec_get_hw_config(decoder_, i);
if (!config) {
LOGGER_WARN(Log::GetLog(), "decoder [{}] does not support device type [{}]", decoder_->name, av_hwdevice_get_type_name(hw_type_));
return -1;
}
//AV_CODEC_HW_CONFIG_METHOD_HW_DEVICE_CTX使用hw_device_ctx API
//hw_type_支持的硬件类型（cuda）
if (config->methods & AV_CODEC_HW_CONFIG_METHOD_HW_DEVICE_CTX &&
config->device_type == hw_type_) {
hw_pix_fmt_ = config->pix_fmt;
break;
}
}
//decoder_ctx_->get_format = &get_hw_format;
decoder_ctx_->pix_fmt = hw_pix_fmt_;
if ((ret = hw_decoder_init(decoder_ctx_, hw_type_)) < 0) {
LOGGER_WARN(Log::GetLog(), "fail to init hw decoder, err [{}]", ret);
return -1;
}
}
ret = avcodec_open2(decoder_ctx_, decoder_, NULL))
...
int VideoParseFFmpeg::hw_decoder_init(AVCodecContext *ctx, const enum AVHWDeviceType type)
{
int err = 0;
if ((err = av_hwdevice_ctx_create(&hw_device_ctx_, type,NULL, NULL, 0)) < 0)
{
LOGGER_WARN(Log::GetLog(), "fail to create specified HW device, err[{}]", AVERROR(err));
char buf[1024] = { 0 };
av_strerror(err, buf, 1024);
return err;
}
//注册硬解码上下文
ctx->hw_device_ctx = av_buffer_ref(hw_device_ctx_);
return err;
}
//解码
//receive_frame以后
if (frame->format == hw_pix_fmt_ &&
hw_enable_ &&
is_hw_support_fmt(pix_fmt_)) {
/* retrieve data from GPU to CPU */
if ((ret = av_hwframe_transfer_data(sw_frame, frame, 0)) < 0) {
LOGGER_WARN(Log::GetLog(), "error transferring the data to system memory, err[{}]", ret);
clear();
return ret;
}
tmp_frame = sw_frame;
} else {
tmp_frame = frame;
}
p_mat_out.push_back(avFrame2Mat(tmp_frame,
avctx,
(AVPixelFormat) tmp_frame->format));
clear();---（end）---
标签：过程 err reads 它的 lock context ble 情况下 打开
原文地址：https://www.cnblogs.com/souther-blog/p/11963422.html
