使用opencv进行视频处理的音频输出
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【中文标题】使用opencv进行视频处理的音频输出【英文标题】:Audio output with video processing with opencv 【发布时间】:2012-01-01 12:45:07 【问题描述】:我正在使用 opencv 处理视频,但同时我需要播放音频并简单地控制它,比如大声或当前帧数。
我想我应该用 ffmpeg 创建一个并行进程,但我不知道该怎么做。你能解释一下该怎么做吗?
或者你知道另一种解决方案吗?
【问题讨论】:
【参考方案1】:我认为在这种情况下应该使用 ffmpeg播放视频的音频和 SDL。
用OpenCV打开文件并处理帧后,您可以使用OpenCV -> SDL
显示它,同时通过ffmpeg检索音频帧并用SDL播放。
Here is a nice collection of ffmpeg/SDL tutorials!
我还发现了一篇不错的帖子,它展示了如何使用 ffmpeg 从视频文件中捕获帧,将它们存储在 OpenCV cv::Mat
中并在 OpenCV 窗口中显示结果。但是这种方式你不能播放音频,因为 OpenCV 不处理。
您可能也有兴趣阅读this post:How to avoid a growing delay with ffmpeg between sound and raw video data ?
编辑:
我花了最后 4 小时编写原型来演示它是如何完成的。 这个demo通过OpenCV读取视频帧(这样你就可以处理它们了)通过ffmpeg读取音频,两者都使用SDL来播放!您必须注意此演示中有 2 个限制:1 - 它假设您正在使用打包为 BGR(24 位)的 OpenCV 图像,以及 2 - 音频和视频没有同步!是的,我留下了一些工作要你做(yeeeey)。不过不要慌,page 6 有一些想法!
sync audio and video 很重要,因为您将对帧进行一些处理,这肯定会使视频和音频快速不同步,因为它们是相互独立播放的。
我上面建议的 ffmpeg 教程对于理解代码非常非常重要,a lot of code from this demo came from there。它们展示了如何处理 SDL,以及如何读取音频/视频流数据包。
#include <highgui.h>
#include <cv.h>
extern "C"
#include <SDL.h>
#include <SDL_thread.h>
#include <avcodec.h>
#include <avformat.h>
#include <iostream>
#include <stdio.h>
//#include <malloc.h>
using namespace cv;
#define SDL_AUDIO_BUFFER_SIZE 1024
typedef struct PacketQueue
AVPacketList *first_pkt, *last_pkt;
int nb_packets;
int size;
SDL_mutex *mutex;
SDL_cond *cond;
PacketQueue;
PacketQueue audioq;
int audioStream = -1;
int videoStream = -1;
int quit = 0;
SDL_Surface* screen = NULL;
SDL_Surface* surface = NULL;
AVFormatContext* pFormatCtx = NULL;
AVCodecContext* aCodecCtx = NULL;
AVCodecContext* pCodecCtx = NULL;
void show_frame(IplImage* img)
if (!screen)
screen = SDL_SetVideoMode(img->width, img->height, 0, 0);
if (!screen)
fprintf(stderr, "SDL: could not set video mode - exiting\n");
exit(1);
// Assuming IplImage packed as BGR 24bits
SDL_Surface* surface = SDL_CreateRGBSurfaceFrom((void*)img->imageData,
img->width,
img->height,
img->depth * img->nChannels,
img->widthStep,
0xff0000, 0x00ff00, 0x0000ff, 0
);
SDL_BlitSurface(surface, 0, screen, 0);
SDL_Flip(screen);
void packet_queue_init(PacketQueue *q)
memset(q, 0, sizeof(PacketQueue));
q->mutex = SDL_CreateMutex();
q->cond = SDL_CreateCond();
int packet_queue_put(PacketQueue *q, AVPacket *pkt)
AVPacketList *pkt1;
if (av_dup_packet(pkt) < 0)
return -1;
//pkt1 = (AVPacketList*) av_malloc(sizeof(AVPacketList));
pkt1 = (AVPacketList*) malloc(sizeof(AVPacketList));
if (!pkt1) return -1;
pkt1->pkt = *pkt;
pkt1->next = NULL;
SDL_LockMutex(q->mutex);
if (!q->last_pkt)
q->first_pkt = pkt1;
else
q->last_pkt->next = pkt1;
q->last_pkt = pkt1;
q->nb_packets++;
q->size += pkt1->pkt.size;
SDL_CondSignal(q->cond);
SDL_UnlockMutex(q->mutex);
return 0;
static int packet_queue_get(PacketQueue *q, AVPacket *pkt, int block)
AVPacketList *pkt1;
int ret;
SDL_LockMutex(q->mutex);
for (;;)
if( quit)
ret = -1;
break;
pkt1 = q->first_pkt;
if (pkt1)
q->first_pkt = pkt1->next;
if (!q->first_pkt)
q->last_pkt = NULL;
q->nb_packets--;
q->size -= pkt1->pkt.size;
*pkt = pkt1->pkt;
//av_free(pkt1);
free(pkt1);
ret = 1;
break;
else if (!block)
ret = 0;
break;
else
SDL_CondWait(q->cond, q->mutex);
SDL_UnlockMutex(q->mutex);
return ret;
int audio_decode_frame(AVCodecContext *aCodecCtx, uint8_t *audio_buf, int buf_size)
static AVPacket pkt;
static uint8_t *audio_pkt_data = NULL;
static int audio_pkt_size = 0;
int len1, data_size;
for (;;)
while (audio_pkt_size > 0)
data_size = buf_size;
len1 = avcodec_decode_audio2(aCodecCtx, (int16_t*)audio_buf, &data_size,
audio_pkt_data, audio_pkt_size);
if (len1 < 0)
/* if error, skip frame */
audio_pkt_size = 0;
break;
audio_pkt_data += len1;
audio_pkt_size -= len1;
if (data_size <= 0)
/* No data yet, get more frames */
continue;
/* We have data, return it and come back for more later */
return data_size;
if (pkt.data)
av_free_packet(&pkt);
if (quit) return -1;
if (packet_queue_get(&audioq, &pkt, 1) < 0) return -1;
audio_pkt_data = pkt.data;
audio_pkt_size = pkt.size;
void audio_callback(void *userdata, Uint8 *stream, int len)
AVCodecContext *aCodecCtx = (AVCodecContext *)userdata;
int len1, audio_size;
static uint8_t audio_buf[(AVCODEC_MAX_AUDIO_FRAME_SIZE * 3) / 2];
static unsigned int audio_buf_size = 0;
static unsigned int audio_buf_index = 0;
while (len > 0)
if (audio_buf_index >= audio_buf_size)
/* We have already sent all our data; get more */
audio_size = audio_decode_frame(aCodecCtx, audio_buf, sizeof(audio_buf));
if(audio_size < 0)
/* If error, output silence */
audio_buf_size = 1024; // arbitrary?
memset(audio_buf, 0, audio_buf_size);
else
audio_buf_size = audio_size;
audio_buf_index = 0;
len1 = audio_buf_size - audio_buf_index;
if (len1 > len)
len1 = len;
memcpy(stream, (uint8_t *)audio_buf + audio_buf_index, len1);
len -= len1;
stream += len1;
audio_buf_index += len1;
void setup_ffmpeg(char* filename)
if (av_open_input_file(&pFormatCtx, filename, NULL, 0, NULL) != 0)
fprintf(stderr, "FFmpeg failed to open file %s!\n", filename);
exit(-1);
if (av_find_stream_info(pFormatCtx) < 0)
fprintf(stderr, "FFmpeg failed to retrieve stream info!\n");
exit(-1);
// Dump information about file onto standard error
dump_format(pFormatCtx, 0, filename, 0);
// Find the first video stream
int i = 0;
for (i; i < pFormatCtx->nb_streams; i++)
if (pFormatCtx->streams[i]->codec->codec_type == CODEC_TYPE_VIDEO && videoStream < 0)
videoStream = i;
if (pFormatCtx->streams[i]->codec->codec_type == CODEC_TYPE_AUDIO && audioStream < 0)
audioStream = i;
if (videoStream == -1)
fprintf(stderr, "No video stream found in %s!\n", filename);
exit(-1);
if (audioStream == -1)
fprintf(stderr, "No audio stream found in %s!\n", filename);
exit(-1);
// Get a pointer to the codec context for the audio stream
aCodecCtx = pFormatCtx->streams[audioStream]->codec;
// Set audio settings from codec info
SDL_AudioSpec wanted_spec;
wanted_spec.freq = aCodecCtx->sample_rate;
wanted_spec.format = AUDIO_S16SYS;
wanted_spec.channels = aCodecCtx->channels;
wanted_spec.silence = 0;
wanted_spec.samples = SDL_AUDIO_BUFFER_SIZE;
wanted_spec.callback = audio_callback;
wanted_spec.userdata = aCodecCtx;
SDL_AudioSpec spec;
if (SDL_OpenAudio(&wanted_spec, &spec) < 0)
fprintf(stderr, "SDL_OpenAudio: %s\n", SDL_GetError());
exit(-1);
AVCodec* aCodec = avcodec_find_decoder(aCodecCtx->codec_id);
if (!aCodec)
fprintf(stderr, "Unsupported codec!\n");
exit(-1);
avcodec_open(aCodecCtx, aCodec);
// audio_st = pFormatCtx->streams[index]
packet_queue_init(&audioq);
SDL_PauseAudio(0);
// Get a pointer to the codec context for the video stream
pCodecCtx = pFormatCtx->streams[videoStream]->codec;
// Find the decoder for the video stream
AVCodec* pCodec = avcodec_find_decoder(pCodecCtx->codec_id);
if (pCodec == NULL)
fprintf(stderr, "Unsupported codec!\n");
exit(-1); // Codec not found
// Open codec
if (avcodec_open(pCodecCtx, pCodec) < 0)
fprintf(stderr, "Unsupported codec!\n");
exit(-1); // Could not open codec
int main(int argc, char* argv[])
if (argc < 2)
std::cout << "Usage: " << argv[0] << " <video>" << std::endl;
return -1;
av_register_all();
// Init SDL
if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER))
fprintf(stderr, "Could not initialize SDL - %s\n", SDL_GetError());
return -1;
// Init ffmpeg and setup some SDL stuff related to Audio
setup_ffmpeg(argv[1]);
VideoCapture cap(argv[1]); // open the default camera
if (!cap.isOpened()) // check if we succeeded
std::cout << "Failed to load file!" << std::endl;
return -1;
AVPacket packet;
while (av_read_frame(pFormatCtx, &packet) >= 0)
if (packet.stream_index == videoStream)
// Actually this is were SYNC between audio/video would happen.
// Right now I assume that every VIDEO packet contains an entire video frame, and that's not true. A video frame can be made by multiple packets!
// But for the time being, assume 1 video frame == 1 video packet,
// so instead of reading the frame through ffmpeg, I read it through OpenCV.
Mat frame;
cap >> frame; // get a new frame from camera
// do some processing on the frame, either as a Mat or as IplImage.
// For educational purposes, applying a lame grayscale conversion
IplImage ipl_frame = frame;
for (int i = 0; i < ipl_frame.width * ipl_frame.height * ipl_frame.nChannels; i += ipl_frame.nChannels)
ipl_frame.imageData[i] = (ipl_frame.imageData[i] + ipl_frame.imageData[i+1] + ipl_frame.imageData[i+2])/3; //B
ipl_frame.imageData[i+1] = (ipl_frame.imageData[i] + ipl_frame.imageData[i+1] + ipl_frame.imageData[i+2])/3; //G
ipl_frame.imageData[i+2] = (ipl_frame.imageData[i] + ipl_frame.imageData[i+1] + ipl_frame.imageData[i+2])/3; //R
// Display it on SDL window
show_frame(&ipl_frame);
av_free_packet(&packet);
else if (packet.stream_index == audioStream)
packet_queue_put(&audioq, &packet);
else
av_free_packet(&packet);
SDL_Event event;
SDL_PollEvent(&event);
switch (event.type)
case SDL_QUIT:
SDL_FreeSurface(surface);
SDL_Quit();
break;
default:
break;
// the camera will be deinitialized automatically in VideoCapture destructor
// Close the codec
avcodec_close(pCodecCtx);
// Close the video file
av_close_input_file(pFormatCtx);
return 0;
在我的 Mac 上,我使用以下代码编译它:
g++ ffmpeg_snd.cpp -o ffmpeg_snd -D_GNU_SOURCE=1 -D_THREAD_SAFE -I/usr/local/include/opencv -I/usr/local/include -I/usr/local/include/SDL -Wl,-framework,Cocoa -L/usr/local/lib -lopencv_core -lopencv_imgproc -lopencv_highgui -lopencv_ml -lopencv_video -lopencv_features2d -lopencv_calib3d -lopencv_objdetect -lopencv_contrib -lopencv_legacy -lopencv_flann -lSDLmain -lSDL -L/usr/local/lib -lavfilter -lavcodec -lavformat -I/usr/local/Cellar/ffmpeg/HEAD/include/libavcodec -I/usr/local/Cellar/ffmpeg/HEAD/include/libavformat
【讨论】:
@victor1234 我正在等待您的反馈。 我现在才有时间回答)) karlphillip,感谢您的代码,它对我也很有帮助。然而,在我的情况下,我管理帧速率,此时我还没有弄清楚如何正确地做到这一点。声音播放中断,音频驱动程序抱怨 ALSA lib pcm.c:7223:(snd_pcm_recover) underrun 我可能会弄清楚,但如果您仍在阅读任何想法,将不胜感激。 一些本应是 cmets 的答案是不再存在的 cookie 帐户。我无法转换它们,因为生成的评论没有有效的所有者。以上是关于使用opencv进行视频处理的音频输出的主要内容,如果未能解决你的问题,请参考以下文章
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