Recherche avancée
Autres articles (78)
-
Organiser par catégorie
17 mai 2013, parDans MédiaSPIP, une rubrique a 2 noms : catégorie et rubrique.
Les différents documents stockés dans MédiaSPIP peuvent être rangés dans différentes catégories. On peut créer une catégorie en cliquant sur "publier une catégorie" dans le menu publier en haut à droite ( après authentification ). Une catégorie peut être rangée dans une autre catégorie aussi ce qui fait qu’on peut construire une arborescence de catégories.
Lors de la publication prochaine d’un document, la nouvelle catégorie créée sera proposée (...) -
Récupération d’informations sur le site maître à l’installation d’une instance
26 novembre 2010, parUtilité
Sur le site principal, une instance de mutualisation est définie par plusieurs choses : Les données dans la table spip_mutus ; Son logo ; Son auteur principal (id_admin dans la table spip_mutus correspondant à un id_auteur de la table spip_auteurs)qui sera le seul à pouvoir créer définitivement l’instance de mutualisation ;
Il peut donc être tout à fait judicieux de vouloir récupérer certaines de ces informations afin de compléter l’installation d’une instance pour, par exemple : récupérer le (...) -
Publier sur MédiaSpip
13 juin 2013Puis-je poster des contenus à partir d’une tablette Ipad ?
Oui, si votre Médiaspip installé est à la version 0.2 ou supérieure. Contacter au besoin l’administrateur de votre MédiaSpip pour le savoir
Sur d’autres sites (5944)
-
FFMPEG : AV out of sync when writing a part of a video to a new file
30 mars 2017, par IT_LaymanI’m developing a data preprocessing program for a computer vision project using FFMPEG and Face detection API. In this program, I need to extract the shots that contain human faces from a given input video file and output them into a new file. But when I played the output video file generated by that program, the video and audio track was out of sync. I think a possible reason is that the timestamp of video frame or audio frame is set incorrectly, but I can’t fix it by myself as I’m not very familiar with FFMPEG library, Please help me solving this out-of-sync issue.
To simplify the code shown below, I have removed all face detection code and use an empty function called
faceDetectto represent it instead.// ffmpegAPI.cpp : Defines the entry point for the console application.
//
#include "stdafx.h"
#include <iostream>
extern "C" {
#include <libavutil></libavutil>opt.h>
#include <libavcodec></libavcodec>avcodec.h>
#include <libavformat></libavformat>avformat.h>
#include <libavutil></libavutil>avutil.h>
#include <libavutil></libavutil>channel_layout.h>
#include <libavutil></libavutil>common.h>
#include <libavutil></libavutil>imgutils.h>
#include <libavutil></libavutil>mathematics.h>
#include <libavutil></libavutil>samplefmt.h>
#include <libavutil></libavutil>pixdesc.h>
#include <libswscale></libswscale>swscale.h>
}
bool faceDetect(AVFrame *frame)
{
/*...*/
return true;
}
int main(int argc, char **argv)
{
int64_t videoPts = 0, audioPts = 0;
int samples_count = 0;
AVFormatContext *ifmt_ctx = NULL, *ofmt_ctx = NULL;
AVOutputFormat *ofmt = NULL;
AVPacket pkt;
AVFrame *frame = NULL;
int videoindex = -1; int audioindex = -1;
double videoTime = DBL_MAX;
const char *in_filename, *out_filename;
int ret, i;
in_filename = "C:\\input.flv";//Input file name
out_filename = "C:\\output.avi";//Output file name
av_register_all();
//Open input file
if ((ret = avformat_open_input(&ifmt_ctx, in_filename, 0, 0)) < 0) {
fprintf(stderr, "Could not open input file '%s'", in_filename);
goto end;
}
//Find input streams
if ((ret = avformat_find_stream_info(ifmt_ctx, 0)) < 0) {
fprintf(stderr, "Failed to retrieve input stream information");
goto end;
}
//Retrive AV stream information
for (i = 0; i < ifmt_ctx->nb_streams; i++)
{
AVStream *stream;
AVCodecContext *codec_ctx;
stream = ifmt_ctx->streams[i];//Get current stream
codec_ctx = stream->codec;//Get current stream codec
if (codec_ctx->codec_type == AVMEDIA_TYPE_VIDEO)
{
videoindex = i;//video stream index
}
else if (codec_ctx->codec_type == AVMEDIA_TYPE_AUDIO)
{
audioindex = i;//audio stream index
}
if (videoindex == -1)//no video stream is found
{
printf("can't find video stream\n");
goto end;
}
}
av_dump_format(ifmt_ctx, 0, in_filename, 0);
//Configure output
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;
}
ofmt = ofmt_ctx->oformat;
//Configure output streams
for (i = 0; i < ifmt_ctx->nb_streams; i++) {//Traversal input streams
AVStream *in_stream = ifmt_ctx->streams[i];//Get current stream
AVStream *out_stream = avformat_new_stream(ofmt_ctx, in_stream->codec->codec);//Create a corresponding output stream
if (!out_stream) {
fprintf(stderr, "Failed allocating output stream\n");
ret = AVERROR_UNKNOWN;
goto end;
}
//Copy codec from current input stream to corresponding output stream
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;
}
if (i == videoindex)//Video stream
{
if (out_stream->codec->codec_id == AV_CODEC_ID_H264)
{
out_stream->codec->me_range = 16;
out_stream->codec->max_qdiff = 4;
out_stream->codec->qmin = 10;
out_stream->codec->qmax = 51;
out_stream->codec->qcompress = 1;
}
}
AVCodecContext *codec_ctx = out_stream->codec;
if (codec_ctx->codec_type == AVMEDIA_TYPE_VIDEO
|| codec_ctx->codec_type == AVMEDIA_TYPE_AUDIO) {
//Find codec encoder
AVCodec *encoder = avcodec_find_encoder(codec_ctx->codec_id);
if (!encoder) {
av_log(NULL, AV_LOG_FATAL, "Necessary encoder not found\n");
ret = AVERROR_INVALIDDATA;
goto end;
}
//Open encoder
ret = avcodec_open2(codec_ctx, encoder, NULL);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Cannot open video encoder for stream #%u\n", i);
goto end;
}
out_stream->codec->codec_tag = 0;
if (ofmt_ctx->oformat->flags & AVFMT_GLOBALHEADER)
out_stream->codec->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
}
//Open the decoder for input stream
codec_ctx = in_stream->codec;
if (codec_ctx->codec_type == AVMEDIA_TYPE_VIDEO
|| codec_ctx->codec_type == AVMEDIA_TYPE_AUDIO) {
ret = avcodec_open2(codec_ctx,
avcodec_find_decoder(codec_ctx->codec_id), NULL);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Failed to open decoder for stream #%u\n", i);
}
}
}
av_dump_format(ofmt_ctx, 0, out_filename, 1);
//Open output file for writing
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 video header
ret = avformat_write_header(ofmt_ctx, NULL);
if (ret < 0) {
fprintf(stderr, "Error occurred when opening output file\n");
goto end;
}
//Write frames in a loop
while (1) {
AVStream *in_stream, *out_stream;
//Read one frame from the input file
ret = av_read_frame(ifmt_ctx, &pkt);
if (ret < 0)
break;
in_stream = ifmt_ctx->streams[pkt.stream_index];//Get current input stream
out_stream = ofmt_ctx->streams[pkt.stream_index];//Get current output stream
if (pkt.stream_index == videoindex)//video frame
{
int got_frame;
frame = av_frame_alloc();
if (!frame) {
ret = AVERROR(ENOMEM);
break;
}
//Readjust packet timestamp for decoding
av_packet_rescale_ts(&pkt,
in_stream->time_base,
in_stream->codec->time_base);
//Decode video frame
int len = avcodec_decode_video2(in_stream->codec, frame, &got_frame, &pkt);
if (len < 0)
{
av_frame_free(&frame);
av_log(NULL, AV_LOG_ERROR, "Decoding failed\n");
break;
}
if (got_frame)//Got a decoded video frame
{
int64_t pts = av_frame_get_best_effort_timestamp(frame);
//determine if the frame image contains human face
bool result = faceDetect(frame);
if (result) //face contained
{
videoTime = pts* av_q2d(out_stream->time_base);
frame->pts = videoPts++;//Set pts of video frame
AVPacket enc_pkt;
av_log(NULL, AV_LOG_INFO, "Encoding video frame\n");
//Create packet for encoding
enc_pkt.data = NULL;
enc_pkt.size = 0;
av_init_packet(&enc_pkt);
//Encoding frame
ret = avcodec_encode_video2(out_stream->codec, &enc_pkt,
frame, &got_frame);
av_frame_free(&frame);
if (!(got_frame))
ret = 0;
/* Configure encoding properties */
enc_pkt.stream_index = videoindex;
av_packet_rescale_ts(&enc_pkt,
out_stream->codec->time_base,
out_stream->time_base);
av_log(NULL, AV_LOG_DEBUG, "Muxing frame\n");
/* Write encoded frame */
ret = av_interleaved_write_frame(ofmt_ctx, &enc_pkt);
if (ret < 0)
break;
}
else //no face contained
{
//Set the videoTime as maximum double value,
//making the corresponding audio frame not been processed
if (videoTime < DBL_MAX)
videoTime = DBL_MAX;
}
}
else
{
av_frame_free(&frame);
}
}
else//Audio frame
{
//Get current frame time
double audioTime = pkt.pts * av_q2d(in_stream->time_base);
if (audioTime >= videoTime)
{//The current frame should be written into output file
int got_frame;
frame = av_frame_alloc();
if (!frame) {
ret = AVERROR(ENOMEM);
break;
}
//Readjust packet timestamp for decoding
av_packet_rescale_ts(&pkt,
in_stream->time_base,
in_stream->codec->time_base);
//Decode audio frame
int len = avcodec_decode_audio4(in_stream->codec, frame, &got_frame, &pkt);
if (len < 0)
{
av_frame_free(&frame);
av_log(NULL, AV_LOG_ERROR, "Decoding failed\n");
break;
}
if (got_frame)//Got a decoded audio frame
{
//Set pts of audio frame
frame->pts = audioPts;
audioPts += frame->nb_samples;
AVPacket enc_pkt;
av_log(NULL, AV_LOG_INFO, "Encoding audio frame");
//Create packet for encoding
enc_pkt.data = NULL;
enc_pkt.size = 0;
av_init_packet(&enc_pkt);
//Encode audio frame
ret = avcodec_encode_audio2(out_stream->codec, &enc_pkt,
frame, &got_frame);
av_frame_free(&frame);
if (!(got_frame))
ret = 0;
/* Configure encoding properties */
enc_pkt.stream_index = audioindex;
av_packet_rescale_ts(&enc_pkt,
out_stream->codec->time_base,
out_stream->time_base);
av_log(NULL, AV_LOG_DEBUG, "Muxing frame\n");
/* Write encoded frame */
ret = av_interleaved_write_frame(ofmt_ctx, &enc_pkt);
if (ret < 0)
break;
}
else //Shouldn't be written
{
av_frame_free(&frame);
}
}
}
av_packet_unref(&pkt);
}
//Write video trailer
av_write_trailer(ofmt_ctx);
end://Clean up
av_log(NULL, AV_LOG_INFO, "Clean up\n");
av_frame_free(&frame);
for (i = 0; i < ifmt_ctx->nb_streams; i++) {
avcodec_close(ifmt_ctx->streams[i]->codec);
if (ofmt_ctx && ofmt_ctx->nb_streams > i && ofmt_ctx->streams[i] && ofmt_ctx->streams[i]->codec)
avcodec_close(ofmt_ctx->streams[i]->codec);
}
avformat_close_input(&ifmt_ctx);
/* Close output file */
if (ofmt_ctx && !(ofmt_ctx->oformat->flags & AVFMT_NOFILE))
avio_closep(&ofmt_ctx->pb);
avformat_free_context(ofmt_ctx);
if (ret < 0 && ret != AVERROR_EOF) {
char buf[256];
av_strerror(ret, buf, sizeof(buf));
av_log(NULL, AV_LOG_ERROR, "Error occurred:%s\n", buf);
system("Pause");
return 1;
}
//Program end
printf("The End.\n");
system("Pause");
return 0;
}
</iostream> -
Révision 23459 : Arrêter le traitement d’image dès que ça coince qq part.
6 mars 2017, par esj@rezo.net -
Stream part of the screen on linux
1er juin 2014, par Boris BrodskiHow can I stream part of my screen using ffmpeg (avconv) on Linux ?
I can record part of my screen :
ffmpeg -f alsa -ac 1 -i pulse -acodec pcm_s16le -f x11grab -r 24 -s 100x200 -i :0.0+20,30 ...But trying to stream it adding
-f rtp rtp://127.0.0.1:1234doesn’t work. ffmpeg starts to stream, but ffplay complains
$ ffplay rtp://127.0.0.1:1234
[rtp @ 0xaf8026a0] Unable to receive RTP payload type 96 without an SDP file describing it
[rtp @ 0xaf8026a0] Estimating duration from bitrate, this may be inaccurate
Input #0, rtp, from 'rtp://127.0.0.1:8080':
Duration: N/A, bitrate: N/A
rtp://127.0.0.1:8080: could not open codecs
1401611400.39 A-V: 0.000 s:0.0 aq= 0KB vq= 0KB sq= 0B f=0/0What do I missing ?
Syndiquer tout le site
