title: ffmpeg_sample解读_qsvdec
date: 2020-10-28 10:15:02
tags: [读书笔记]
typora-copy-images-to: ./imgs
typora-root-url: ./imgs
总结
读取视频流.解码出视频帧后进行处理.使用了硬件编码,最后写出文件的过程
流程图
graph TB
afoi[avformat_open_input]
-->ahcc[av_hwdevice_ctx_create]
-->acfdbn[avcodec_find_decoder_by_name]
-->aac[avcodec_alloc_context3]
-->aco[avcodec_open2]
-->ao[avio_open]
-->afa[av_frame_alloc]
-->arf{av_read_frame>0?}
-->|no|release[release]
arf-->|yes|dp[decode_packet]
-->acsp[avcodec_send_packet]
-->acrf[avcodec_receive_frame]
-->aw[avio_write]
-->release
image-20201030152827979
代码
/**
* @file
* Intel QSV-accelerated H.264 decoding example.
*
* @example qsvdec.c
* This example shows how to do QSV-accelerated H.264 decoding with output
* frames in the GPU video surfaces.
*/
//#include "config.h"
#include
#include "libavformat/avformat.h"
#include "libavformat/avio.h"
#include "libavcodec/avcodec.h"
#include "libavutil/buffer.h"
#include "libavutil/error.h"
#include "libavutil/hwcontext.h"
//#include "libavutil/hwcontext_qsv.h"
#include "libavutil/mem.h"
typedef struct DecodeContext {
AVBufferRef *hw_device_ref;
} DecodeContext;
static int get_format(AVCodecContext *avctx, const enum AVPixelFormat *pix_fmts) {
while (*pix_fmts != AV_PIX_FMT_NONE) {
if (*pix_fmts == AV_PIX_FMT_QSV) {
DecodeContext *decode = avctx->opaque;
AVHWFramesContext *frames_ctx;
// AVQSVFramesContext *frames_hwctx;
int ret;
/* create a pool of surfaces to be used by the decoder */
avctx->hw_frames_ctx = av_hwframe_ctx_alloc(decode->hw_device_ref);
if (!avctx->hw_frames_ctx)
return AV_PIX_FMT_NONE;
frames_ctx = (AVHWFramesContext *) avctx->hw_frames_ctx->data;
// frames_hwctx = frames_ctx->hwctx;
frames_ctx->format = AV_PIX_FMT_QSV;
frames_ctx->sw_format = avctx->sw_pix_fmt;
frames_ctx->width = FFALIGN(avctx->coded_width, 32);
frames_ctx->height = FFALIGN(avctx->coded_height, 32);
frames_ctx->initial_pool_size = 32;
// frames_hwctx->frame_type = MFX_MEMTYPE_VIDEO_MEMORY_DECODER_TARGET;
ret = av_hwframe_ctx_init(avctx->hw_frames_ctx);
if (ret < 0)
return AV_PIX_FMT_NONE;
return AV_PIX_FMT_QSV;
}
pix_fmts++;
}
fprintf(stderr, "The QSV pixel format not offered in get_format()\n");
return AV_PIX_FMT_NONE;
}
/**
* 解码数据报
* @param decode
* @param decoder_ctx
* @param frame
* @param sw_frame
* @param pkt
* @param output_ctx
* @return
*/
static int decode_packet(DecodeContext *decode, AVCodecContext *decoder_ctx,
AVFrame *frame, AVFrame *sw_frame,
AVPacket *pkt, AVIOContext *output_ctx) {
int ret = 0;
//数据送入解码器,获取解码后的帧
ret = avcodec_send_packet(decoder_ctx, pkt);
if (ret < 0) {
fprintf(stderr, "Error during decoding\n");
return ret;
}
while (ret >= 0) {
int i, j;
//取出解码帧
ret = avcodec_receive_frame(decoder_ctx, frame);
if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
break;
else if (ret < 0) {
fprintf(stderr, "Error during decoding\n");
return ret;
}
/* A real program would do something useful with the decoded frame here.
* We just retrieve the raw data and write it to a file, which is rather
* useless but pedagogic. */
//解码后的帧经过硬件转换
ret = av_hwframe_transfer_data(sw_frame, frame, 0);
if (ret < 0) {
fprintf(stderr, "Error transferring the data to system memory\n");
goto fail;
}
for (i = 0; i < FF_ARRAY_ELEMS(sw_frame->data) && sw_frame->data[i]; i++)
for (j = 0; j < (sw_frame->height >> (i > 0)); j++)
//把数据写出到ouput上下文
avio_write(output_ctx, sw_frame->data[i] + j * sw_frame->linesize[i],
sw_frame->width);
fail:
av_frame_unref(sw_frame);
av_frame_unref(frame);
if (ret < 0)
return ret;
}
return 0;
}
/**
*读取视频流.解码出视频帧后进行处理.使用了硬件编码
* @param argc
* @param argv
* @return
*/
int qsvdec_main(int argc, char **argv) {
AVFormatContext *input_ctx = NULL;
AVStream *video_st = NULL;
AVCodecContext *decoder_ctx = NULL;
const AVCodec *decoder;
AVPacket pkt = {0};
AVFrame *frame = NULL, *sw_frame = NULL;
DecodeContext decode = {NULL};
AVIOContext *output_ctx = NULL;
int ret, i;
if (argc < 3) {
fprintf(stderr, "Usage: %s