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Video d’abeille en portrait
14 mai 2011, par
Mis à jour : Février 2012
Langue : français
Type : Video
Autres articles (86)
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Les tâches Cron régulières de la ferme
1er décembre 2010, parLa gestion de la ferme passe par l’exécution à intervalle régulier de plusieurs tâches répétitives dites Cron.
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Cette tâche, planifiée chaque minute, a pour simple effet d’appeler le Cron de l’ensemble des instances de la mutualisation régulièrement. Couplée avec un Cron système sur le site central de la mutualisation, cela permet de simplement générer des visites régulières sur les différents sites et éviter que les tâches des sites peu visités soient trop (...) -
MediaSPIP 0.1 Beta version
25 avril 2011, parMediaSPIP 0.1 beta is the first version of MediaSPIP proclaimed as "usable".
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To get a working installation, you must manually install all-software dependencies on the server.
If you want to use this archive for an installation in "farm mode", you will also need to proceed to other manual (...) -
Submit bugs and patches
13 avril 2011Unfortunately a software is never perfect.
If you think you have found a bug, report it using our ticket system. Please to help us to fix it by providing the following information : the browser you are using, including the exact version as precise an explanation as possible of the problem if possible, the steps taken resulting in the problem a link to the site / page in question
If you think you have solved the bug, fill in a ticket and attach to it a corrective patch.
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Sur d’autres sites (8869)
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doc/resampler, swresample/options : use proper capitalization
10 octobre 2015, par Ganesh Ajjanagaddedoc/resampler, swresample/options : use proper capitalization
Proper names should be capitalized in all user facing API as far as
possible. The option names themselves have not been changed since :
1. We consistently keep option names in lower case.
2. Changing them would break existing scripts.
3. I suspect that we want to be similar to Sox and its relevant options.The converse is also true : improper names should not be capitalized
generally.Signed-off-by : Ganesh Ajjanagadde <gajjanagadde@gmail.com>
Signed-off-by : Michael Niedermayer <michael@niedermayer.cc> -
avutil/dict : Improve documentation
24 septembre 2022, par Marvin Scholz -
ffmpeg decoding through C-API leads to artefacts when input resolution is 1200x1600. Am I doing something wrong ?
26 février 2023, par AntonioUsing the C-API and FFmpeg 5.1 I have been able to encode h264 videos with libx264 on Android.
Now I wanted to replay them on Linux inside my C++ application. These videos can be played correctly on a browser, or on other players that I tried like mplayer or ffplay from ffmpeg. Also, I can unroll the frames with
ffmpeg -i recording.mp4 -start_number 0 -qscale:v 5 %06d.jpgand the images look alright.

However in my C++ application every now and then, but in a very repeatable way, I get artifacts (like the bright pixels showing up above the monitor). They do not accumulate, even though they are not related to keyframes. So whatever error is going on, it doesn't seem to have an impact on subsequent frames. I use OpenCV to visualize the output, and I am pretty sure the problem is not the conversion to BGR because the artifact is already there if I simply show the y channel (luminance, grayscale).


These artifacts show up in videos that I have recorded with a 1200x1600 resolution. It is to be noted that 1200 is not divisible by 32 so ffmpeg does add some padding, but I am dealing with it and it's not an issue. Videos recorded at 1920x1440 are replayed with no artifacts. Two sample videos can be found here for download.


Here follows the code I am using, on the bottom you can see a picture of my decoded image with the artifact and the same as unrolled by ffmpeg command line. It should be noted that I am working with a custom built version of ffmpeg, out of conan packages, while the unrolling is done with ffmpeg from command line that comes with Ubuntu.


extern "C" {
#include <libavcodec></libavcodec>avcodec.h>
#include <libavformat></libavformat>avformat.h>
}

#include 
#include 
#include 

#include <iostream>
int main(int argc, char** argv) {

 int ret;

 auto pkt = av_packet_alloc();
 if (!pkt) {
 std::cerr << "Failed av_packet_alloc()" << std::endl;
 exit(1);
 }

 AVFormatContext* av_format = avformat_alloc_context();
 ret = avformat_open_input(&av_format, FILE_NAME, nullptr, nullptr);
 if (ret < 0) {
 std::cerr << "Failed avformat_open_input, Error: " << ret << std::endl;
 ///Error codes https://stackoverflow.com/questions/12780931/ffmpeg-exit-status-1094995529
 exit(1);
 }
 av_dump_format(av_format, 0, FILE_NAME, 0);
 auto video_st_number = av_find_best_stream(av_format, AVMEDIA_TYPE_VIDEO, -1, -1, nullptr, 0);
 if (video_st_number < 0) {
 std::cerr << "av_find_best_stream couldn't find video stream" << std::endl;
 exit(1);
 }
 auto video_st = av_format->streams[video_st_number];
 auto codec_id = video_st->codecpar->codec_id;
 std::cout << "Duration " << video_st->duration << std::endl;
 std::cout << "n_frames " << video_st->nb_frames << std::endl;

 auto frame = av_frame_alloc();
 if (!frame) {
 fprintf(stderr, "Could not allocate video frame\n");
 exit(1);
 }

 auto codec = avcodec_find_decoder(codec_id);
 if (!codec) {
 fprintf(stderr, "Codec not found\n");
 exit(1);
 }

 auto c = avcodec_alloc_context3(codec);
 if (!c) {
 fprintf(stderr, "Could not allocate video codec context\n");
 exit(1);
 }


 if ((ret = avcodec_parameters_to_context(c, video_st->codecpar))) {
 fprintf(stderr, "Failed avcodec_parameters_to_context\n");
 exit(1);
 }

 c->pix_fmt = AV_PIX_FMT_YUV420P;///Not really necessary
 c->thread_count = 1;///No impact

 /* open it */
 if (avcodec_open2(c, codec, NULL) < 0) {
 fprintf(stderr, "Could not open codec\n ");
 exit(1);
 }

 std::size_t counter = 0;
 std::size_t n_keyframes = 0;

 while (ret >= 0) {
 ret = av_read_frame(av_format, pkt);
 if (pkt->size == 0) {
 std::cout << "Skipping packet of size zero" << std::endl;
 av_packet_unref(pkt);
 continue;
 }
 while (avcodec_send_packet(c, pkt) != 0) {
 if (avcodec_receive_frame(c, frame) != 0) {
 std::cerr << "Error receiving frame" << std::endl;
 exit(1);
 } else {
 n_keyframes += frame->key_frame;
 std::cout << "Decoded " << ++counter << " frames. Frame No. " << frame->pts / pkt->duration << " "
 << frame->decode_error_flags << " " << frame->key_frame << " " << n_keyframes << " "
 << frame->pkt_dts << std::endl;
 }
 display(frame);
 }
 av_packet_unref(pkt);
 }

 avcodec_send_packet(c, nullptr);
 std::cout << "Flushing decoder" << std::endl;

 while (avcodec_receive_frame(c, frame) == 0) {
 n_keyframes += frame->key_frame;
 std::cout << "Decoded " << ++counter << " frames. Frame No. " << frame->pts << " " << frame->decode_error_flags
 << " " << frame->key_frame << " " << n_keyframes << " " << frame->pkt_dts << std::endl;

 display(frame);
 }

 avcodec_free_context(&c);
 avformat_free_context(av_format);
 av_frame_free(&frame);
 av_packet_free(&pkt);

 return 0;
}
</iostream>




For completeness, this is the
displayfunction, using openCV

void display(const AVFrame* frame) {
 static std::vector yuv_buffer;
 yuv_buffer.resize(frame->linesize[0] * 3 / 2 * frame->width);
 cv::Mat mYUV(frame->height * 3 / 2, frame->width, CV_8UC1, yuv_buffer.data(), frame->linesize[0]);
 memcpy(mYUV.ptr(), frame->data[0], frame->linesize[0] * frame->height);
 //cv::imshow("grayscale", mYUV.rowRange(0, frame->height));
 //cv::imshow("u", cv::Mat(frame->height / 2, frame->width / 2, CV_8UC1, frame->data[1], frame->linesize[1]));
 //cv::imshow("v", cv::Mat(frame->height / 2, frame->width / 2, CV_8UC1, frame->data[2], frame->linesize[2]));

 int dest_row = frame->height;
 for (int j = 0; j < frame->height / 2; j++) {
 memcpy(mYUV.ptr(dest_row), frame->data[1] + frame->linesize[1] * j, frame->width);
 j++;
 memcpy(mYUV.ptr(dest_row) + frame->width / 2, frame->data[1] + frame->linesize[1] * j, frame->width);
 dest_row++;
 }
 for (int j = 0; j < frame->height / 2; j++) {
 memcpy(mYUV.ptr(dest_row), frame->data[2] + frame->linesize[2] * j, frame->width);
 j++;
 memcpy(mYUV.ptr(dest_row) + frame->width / 2, frame->data[2] + frame->linesize[2] * j, frame->width);
 dest_row++;
 }
 cv::Mat mRGB(frame->height, frame->width, CV_8UC3);
 cvtColor(mYUV, mRGB, cv::COLOR_YUV2BGR_I420, 3);
 cv::imshow("Video", mRGB);
 cv::waitKey(0);
}



Note : The
AVFrame->cv::Matconverter is now available in corrected version as answer here.

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