我想将处理应用于带有声道的视频片段，逐帧提取和处理，并将结果写入输出文件。输出剪辑中的帧数，帧大小和速度保持不变。另外，我想保留与源中相同的音轨。
我可以使用opencv读取剪辑，解码帧和处理。音频数据包也写得很好。我坚持形成输出视频流。
我现在拥有的最小可运行代码（抱歉它不是那么短，但不能缩短）：
extern "C" {
#include <libavutil/timestamp.h>
#include <libavformat/avformat.h>
#include "libavcodec/avcodec.h"
#include <libavutil/opt.h>
#include <libavdevice/avdevice.h>
#include <libswscale/swscale.h>
}
#include "opencv2/opencv.hpp"
#if LIBAVCODEC_VERSION_INT < AV_VERSION_INT(55,28,1)
#define av_frame_alloc avcodec_alloc_frame
#endif
using namespace std;
using namespace cv;
static void log_packet(const AVFormatContext *fmt_ctx, const AVPacket *pkt, const char *tag)
{
AVRational *time_base = &fmt_ctx->streams[pkt->stream_index]->time_base;
char buf1[AV_TS_MAX_STRING_SIZE] = { 0 };
av_ts_make_string(buf1, pkt->pts);
char buf2[AV_TS_MAX_STRING_SIZE] = { 0 };
av_ts_make_string(buf1, pkt->dts);
char buf3[AV_TS_MAX_STRING_SIZE] = { 0 };
av_ts_make_string(buf1, pkt->duration);
char buf4[AV_TS_MAX_STRING_SIZE] = { 0 };
av_ts_make_time_string(buf1, pkt->pts, time_base);
char buf5[AV_TS_MAX_STRING_SIZE] = { 0 };
av_ts_make_time_string(buf1, pkt->dts, time_base);
char buf6[AV_TS_MAX_STRING_SIZE] = { 0 };
av_ts_make_time_string(buf1, pkt->duration, time_base);
printf("pts:%s pts_time:%s dts:%s dts_time:%s duration:%s duration_time:%s stream_index:%d\n",
buf1, buf4,
buf2, buf5,
buf3, buf6,
pkt->stream_index);
}
int main(int argc, char **argv)
{
AVOutputFormat *ofmt = NULL;
AVFormatContext *ifmt_ctx = NULL, *ofmt_ctx = NULL;
AVPacket pkt;
AVFrame *pFrame = NULL;
AVFrame *pFrameRGB = NULL;
int frameFinished = 0;
pFrame = av_frame_alloc();
pFrameRGB = av_frame_alloc();
const char *in_filename, *out_filename;
int ret, i;
in_filename = "../../TestClips/Audio Video Sync Test.mp4";
out_filename = "out.mp4";
// Initialize FFMPEG
av_register_all();
// Get input file format context
if ((ret = avformat_open_input(&ifmt_ctx, in_filename, 0, 0)) < 0)
{
fprintf(stderr, "Could not open input file '%s'", in_filename);
goto end;
}
// Extract streams description
if ((ret = avformat_find_stream_info(ifmt_ctx, 0)) < 0)
{
fprintf(stderr, "Failed to retrieve input stream information");
goto end;
}
// Print detailed information about the input or output format,
// such as duration, bitrate, streams, container, programs, metadata, side data, codec and time base.
av_dump_format(ifmt_ctx, 0, in_filename, 0);
// Allocate an AVFormatContext for an output format.
avformat_alloc_output_context2(&ofmt_ctx, NULL, NULL, out_filename);
if (!ofmt_ctx)
{
fprintf(stderr, "Could not create output context\n");
ret = AVERROR_UNKNOWN;
goto end;
}
// The output container format.
ofmt = ofmt_ctx->oformat;
// Allocating output streams
for (i = 0; i < ifmt_ctx->nb_streams; i++)
{
AVStream *in_stream = ifmt_ctx->streams[i];
AVStream *out_stream = avformat_new_stream(ofmt_ctx, in_stream->codec->codec);
if (!out_stream)
{
fprintf(stderr, "Failed allocating output stream\n");
ret = AVERROR_UNKNOWN;
goto end;
}
ret = avcodec_copy_context(out_stream->codec, in_stream->codec);
if (ret < 0)
{
fprintf(stderr, "Failed to copy context from input to output stream codec context\n");
goto end;
}
out_stream->codec->codec_tag = 0;
if (ofmt_ctx->oformat->flags & AVFMT_GLOBALHEADER)
{
out_stream->codec->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
}
}
// Show output format info
av_dump_format(ofmt_ctx, 0, out_filename, 1);
// Open output file
if (!(ofmt->flags & AVFMT_NOFILE))
{
ret = avio_open(&ofmt_ctx->pb, out_filename, AVIO_FLAG_WRITE);
if (ret < 0)
{
fprintf(stderr, "Could not open output file '%s'", out_filename);
goto end;
}
}
// Write output file header
ret = avformat_write_header(ofmt_ctx, NULL);
if (ret < 0)
{
fprintf(stderr, "Error occurred when opening output file\n");
goto end;
}
// Search for input video codec info
AVCodec *in_codec = nullptr;
AVCodecContext* avctx = nullptr;
int video_stream_index = -1;
for (int i = 0; i < ifmt_ctx->nb_streams; i++)
{
if (ifmt_ctx->streams[i]->codec->coder_type == AVMEDIA_TYPE_VIDEO)
{
video_stream_index = i;
avctx = ifmt_ctx->streams[i]->codec;
in_codec = avcodec_find_decoder(avctx->codec_id);
if (!in_codec)
{
fprintf(stderr, "in codec not found\n");
exit(1);
}
break;
}
}
// Search for output video codec info
AVCodec *out_codec = nullptr;
AVCodecContext* o_avctx = nullptr;
int o_video_stream_index = -1;
for (int i = 0; i < ofmt_ctx->nb_streams; i++)
{
if (ofmt_ctx->streams[i]->codec->coder_type == AVMEDIA_TYPE_VIDEO)
{
o_video_stream_index = i;
o_avctx = ofmt_ctx->streams[i]->codec;
out_codec = avcodec_find_encoder(o_avctx->codec_id);
if (!out_codec)
{
fprintf(stderr, "out codec not found\n");
exit(1);
}
break;
}
}
// openCV pixel format
AVPixelFormat pFormat = AV_PIX_FMT_RGB24;
// Data size
int numBytes = avpicture_get_size(pFormat, avctx->width, avctx->height);
// allocate buffer
uint8_t *buffer = (uint8_t *)av_malloc(numBytes * sizeof(uint8_t));
// fill frame structure
avpicture_fill((AVPicture *)pFrameRGB, buffer, pFormat, avctx->width, avctx->height);
// frame area
int y_size = avctx->width * avctx->height;
// Open input codec
avcodec_open2(avctx, in_codec, NULL);
// Main loop
while (1)
{
AVStream *in_stream, *out_stream;
ret = av_read_frame(ifmt_ctx, &pkt);
if (ret < 0)
{
break;
}
in_stream = ifmt_ctx->streams[pkt.stream_index];
out_stream = ofmt_ctx->streams[pkt.stream_index];
log_packet(ifmt_ctx, &pkt, "in");
// copy packet
pkt.pts = av_rescale_q_rnd(pkt.pts, in_stream->time_base, out_stream->time_base, AVRounding(AV_ROUND_NEAR_INF | AV_ROUND_PASS_MINMAX));
pkt.dts = av_rescale_q_rnd(pkt.dts, in_stream->time_base, out_stream->time_base, AVRounding(AV_ROUND_NEAR_INF | AV_ROUND_PASS_MINMAX));
pkt.duration = av_rescale_q(pkt.duration, in_stream->time_base, out_stream->time_base);
pkt.pos = -1;
log_packet(ofmt_ctx, &pkt, "out");
if (pkt.stream_index == video_stream_index)
{
avcodec_decode_video2(avctx, pFrame, &frameFinished, &pkt);
if (frameFinished)
{
struct SwsContext *img_convert_ctx;
img_convert_ctx = sws_getCachedContext(NULL,
avctx->width,
avctx->height,
avctx->pix_fmt,
avctx->width,
avctx->height,
AV_PIX_FMT_BGR24,
SWS_BICUBIC,
NULL,
NULL,
NULL);
sws_scale(img_convert_ctx,
((AVPicture*)pFrame)->data,
((AVPicture*)pFrame)->linesize,
0,
avctx->height,
((AVPicture *)pFrameRGB)->data,
((AVPicture *)pFrameRGB)->linesize);
sws_freeContext(img_convert_ctx);
// Do some image processing
cv::Mat img(pFrame->height, pFrame->width, CV_8UC3, pFrameRGB->data[0],false);
cv::GaussianBlur(img,img,Size(5,5),3);
cv::imshow("Display", img);
cv::waitKey(5);
// --------------------------------
// Transform back to initial format
// --------------------------------
img_convert_ctx = sws_getCachedContext(NULL,
avctx->width,
avctx->height,
AV_PIX_FMT_BGR24,
avctx->width,
avctx->height,
avctx->pix_fmt,
SWS_BICUBIC,
NULL,
NULL,
NULL);
sws_scale(img_convert_ctx,
((AVPicture*)pFrameRGB)->data,
((AVPicture*)pFrameRGB)->linesize,
0,
avctx->height,
((AVPicture *)pFrame)->data,
((AVPicture *)pFrame)->linesize);
// --------------------------------------------
// Something must be here
// --------------------------------------------
//
// Write fideo frame (How to write frame to output stream ?)
//
// --------------------------------------------
sws_freeContext(img_convert_ctx);
}
}
else // write sound frame
{
ret = av_interleaved_write_frame(ofmt_ctx, &pkt);
}
if (ret < 0)
{
fprintf(stderr, "Error muxing packet\n");
break;
}
// Decrease packet ref counter
av_packet_unref(&pkt);
}
av_write_trailer(ofmt_ctx);
end:
avformat_close_input(&ifmt_ctx);
// close output
if (ofmt_ctx && !(ofmt->flags & AVFMT_NOFILE))
{
avio_closep(&ofmt_ctx->pb);
}
avformat_free_context(ofmt_ctx);
if (ret < 0 && ret != AVERROR_EOF)
{
char buf_err[AV_ERROR_MAX_STRING_SIZE] = { 0 };
av_make_error_string(buf_err, AV_ERROR_MAX_STRING_SIZE, ret);
fprintf(stderr, "Error occurred: %s\n", buf_err);
return 1;
}
avcodec_close(avctx);
av_free(pFrame);
av_free(pFrameRGB);
return 0;
}
答案 0 :(得分：2)
我的原始代码段错误。初始化输出编解码器上下文似乎解决了它。下面的代码对我有用，但我没有测试OpenCV的东西，因为我没有安装lib。
获取编解码器上下文：
// Search for output video codec info
AVCodec *out_codec = NULL;
AVCodecContext* o_avctx = NULL;
int o_video_stream_index = -1;
for (int i = 0; i < ofmt_ctx->nb_streams; i++)
{
if (ofmt_ctx->streams[i]->codec->coder_type == AVMEDIA_TYPE_VIDEO)
{
o_video_stream_index = i;
out_codec = avcodec_find_encoder(ofmt_ctx->streams[i]->codec->codec_id);
o_avctx = avcodec_alloc_context3(out_codec);
o_avctx->height = avctx->height;
o_avctx->width = avctx->width;
o_avctx->sample_aspect_ratio = avctx->sample_aspect_ratio;
if (out_codec->pix_fmts)
o_avctx->pix_fmt = out_codec->pix_fmts[0];
else
o_avctx->pix_fmt = avctx->pix_fmt;
o_avctx->time_base = avctx->time_base;
avcodec_open2(o_avctx, out_codec, NULL);
}
}
编码并写：
// Main loop
while (1)
{
...
if (pkt.stream_index == video_stream_index)
{
avcodec_decode_video2(avctx, pFrame, &frameFinished, &pkt);
if (frameFinished)
{
...
// --------------------------------------------
// Something must be here
// --------------------------------------------
int got_packet = 0;
AVPacket enc_pkt = { 0 };
av_init_packet(&enc_pkt);
avcodec_encode_video2(o_avctx, &enc_pkt, pFrame, &got_packet);
av_interleaved_write_frame(ofmt_ctx, &enc_pkt);
....
}
}
答案 1 :(得分：0)
您应该将已处理帧的数据包信息分配给您的原始数据包，然后将其传递给av_interleaved_write_frame