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Autres articles (50)
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Websites made with MediaSPIP
2 mai 2011, parThis page lists some websites based on MediaSPIP.
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Installation en mode ferme
4 février 2011, parLe mode ferme permet d’héberger plusieurs sites de type MediaSPIP en n’installant qu’une seule fois son noyau fonctionnel.
C’est la méthode que nous utilisons sur cette même plateforme.
L’utilisation en mode ferme nécessite de connaïtre un peu le mécanisme de SPIP contrairement à la version standalone qui ne nécessite pas réellement de connaissances spécifique puisque l’espace privé habituel de SPIP n’est plus utilisé.
Dans un premier temps, vous devez avoir installé les mêmes fichiers que l’installation (...) -
La sauvegarde automatique de canaux SPIP
1er avril 2010, parDans le cadre de la mise en place d’une plateforme ouverte, il est important pour les hébergeurs de pouvoir disposer de sauvegardes assez régulières pour parer à tout problème éventuel.
Pour réaliser cette tâche on se base sur deux plugins SPIP : Saveauto qui permet une sauvegarde régulière de la base de donnée sous la forme d’un dump mysql (utilisable dans phpmyadmin) mes_fichiers_2 qui permet de réaliser une archive au format zip des données importantes du site (les documents, les éléments (...)
Sur d’autres sites (9191)
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lavc/vvc : Validate IBC block vector
25 juin 2024, par Frank Plowmanlavc/vvc : Validate IBC block vector
From H.266 (V3) (09/2023) p. 321 :
It is a requirement of bitstream conformance that the luma block
vector bvL shall obey the following constraints :
CtbSizeY is greater than or equal to
((yCb + (bvL[ 1 ] >> 4)) & (CtbSizeY − 1)) + cbHeightThis patch checks this is true, which fixes crashes on fuzzed
bitstreams.Signed-off-by : Frank Plowman <post@frankplowman.com>
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FFMPEG : how to create a "title slide" for 3 seconds before a video [closed]
15 mars 2024, par ashayI'm trying to make a lecture video to put online. I have the video itself, and I have a title slide that I'd like to play for 3 seconds before the main video.


I tried using ffmpeg to (1) create a 3 second long video from the title slide and (2) concat the two videos together.


I'm having issues concatenating the videos together — when I do so, the resulting video is much longer than it should be. When I look online, others have similar problems — and this seems to occur when the parameters of the two videos do not match perfectly.


I'd prefer to do this without re-encoding the main video — and it seems this should be possible because I should be able to control what parameters are set for the "lecture slide video".


Here are the commands I've run.
The main video has framerate 25, resolution 1920x1080, and an audio stream at #0:0 and a video stream at #0:1 (according to ffmpeg -i [video].


To create the video of the title slide, I ran
ffmpeg -framerate 25 -i lec01_title.png -t 3 -c:v libx264 -x265-params lossless=1 -pix_fmt yuvj420p -vf scale=1920:1080 lec01_title.mp4 -f lavfi -i anullsrc -c:a aac -shortest.
Then to reorder the streams to match the main video, I ranffmpeg -i lec01_title.mp4 -map 0:a -map 0:v -c:v copy -c:a copy lec01_title_matched.mp4.

Then to concatenate the two files together, I created a text file "concat_list" with :

file 'lec01_title_matched.mp4' file 'lec01.mp4', and ran the commandffmpeg -f concat -safe 0 -i concat_list.txt -c copy -movflags +faststart output.mp4.

The main video is 53 minutes long, but the final output video after concatenating is 1 hour and 43 minutes long.


I'm looking for advice for how to create the "lecture title video" properly to match the parameters of the second video so that I can concatenate them without problems.


Here's the output of
ffmpeg -i lec01.mp4:

ffmpeg version 6.1.1 Copyright (c) 2000-2023 the FFmpeg developers
 built with Apple clang version 15.0.0 (clang-1500.1.0.2.5)
 configuration: --prefix=/opt/homebrew/Cellar/ffmpeg/6.1.1 --enable-shared --enable-pthreads --enable-version3 --cc=clang --host-cflags= --host-ldflags='-Wl,-ld_classic' --enable-ffplay --enable-gnutls --enable-gpl --enable-libaom --enable-libaribb24 --enable-libbluray --enable-libdav1d --enable-libharfbuzz --enable-libjxl --enable-libmp3lame --enable-libopus --enable-librav1e --enable-librist --enable-librubberband --enable-libsnappy --enable-libsrt --enable-libsvtav1 --enable-libtesseract --enable-libtheora --enable-libvidstab --enable-libvmaf --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libxvid --enable-lzma --enable-libfontconfig --enable-libfreetype --enable-frei0r --enable-libass --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libspeex --enable-libsoxr --enable-libzmq --enable-libzimg --disable-libjack --disable-indev=jack --enable-videotoolbox --enable-audiotoolbox --enable-neon
 libavutil 58. 29.100 / 58. 29.100
 libavcodec 60. 31.102 / 60. 31.102
 libavformat 60. 16.100 / 60. 16.100
 libavdevice 60. 3.100 / 60. 3.100
 libavfilter 9. 12.100 / 9. 12.100
 libswscale 7. 5.100 / 7. 5.100
 libswresample 4. 12.100 / 4. 12.100
 libpostproc 57. 3.100 / 57. 3.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'dcai_lec01.mp4':
 Metadata:
 major_brand : isom
 minor_version : 512
 compatible_brands: isomiso2avc1mp41
 title : 2-190-wideshot
 encoder : Lavf60.16.100
 Duration: 00:47:39.08, start: 0.000000, bitrate: 1435 kb/s
 Stream #0:0[0x1](und): Audio: aac (LC) (mp4a / 0x6134706D), 96000 Hz, stereo, fltp, 128 kb/s (default)
 Metadata:
 handler_name : SoundHandler
 vendor_id : [0][0][0][0]
 Stream #0:1[0x2](und): Video: h264 (High) (avc1 / 0x31637661), yuvj420p(pc, progressive), 1920x1080 [SAR 1:1 DAR 16:9], 1298 kb/s, 25 fps, 25 tbr, 12800 tbn (default)
 Metadata:
 handler_name : VideoHandler
 vendor_id : [0][0][0][0]
 encoder : Lavc60.31.102 libx264


Described above in detail.


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FFMPEG C Library : Encoding h264 stream into Matroska .mkv container creates corrupt files
16 mars 2024, par Marvin KillingI want to use the FFMPEG C Library to create a Matroska Video .mkv file with only an h264 stream, but the resulting .mkv file comes out corrupt.


The file cannot be played back with Windows Media Player, ffplay, or VLC, and when I try to
ffprobethe resulting file, these are the error messages :

[h264 @ 0000015060d8f5c0] No start code is found.
 Last message repeated 1 times
[h264 @ 0000015060d8f5c0] non-existing PPS 0 referenced
 Last message repeated 1 times
[h264 @ 0000015060d8f5c0] decode_slice_header error
[h264 @ 0000015060d8f5c0] no frame!
[h264 @ 0000015060d8f5c0] non-existing PPS 0 referenced
 Last message repeated 1 times
[h264 @ 0000015060d8f5c0] decode_slice_header error
[h264 @ 0000015060d8f5c0] no frame!
[h264 @ 0000015060d8f5c0] non-existing PPS 0 referenced
 Last message repeated 1 times
# [...]
# this continues for a long time


I have followed the other troubleshooting steps for encoding h264 into Matroska, but none of them seemed to have done the trick for me :


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- Setting
AV_CODEC_FLAG_GLOBAL_HEADER: Invalid data when creating mkv container with h264 stream because extradata is null - Allocating some space for extradata : Initializing an output file for muxing mkv with FFmpeg






This is my C code :


#include 
#include <libavutil></libavutil>opt.h>
#include <libavutil></libavutil>imgutils.h>
#include <libavcodec></libavcodec>avcodec.h>
#include <libavformat></libavformat>avformat.h>

int main(void) {
 char *out_file_path = "./video.mkv";
 AVFormatContext *format_context;
 AVStream *video_stream;
 AVCodecContext *codec_context;

 avformat_alloc_output_context2(&format_context, NULL, NULL, out_file_path);

 const AVCodec *codec = avcodec_find_encoder(AV_CODEC_ID_H264);
 video_stream = avformat_new_stream(format_context, NULL);

 codec_context = avcodec_alloc_context3(codec);
 av_opt_set(codec_context->priv_data, "preset", "superfast", 0);
 av_opt_set(codec_context->priv_data, "crf", "22", 0);

 codec_context->width = 1920;
 codec_context->height = 1080;
 codec_context->time_base = av_make_q(1, 30);
 codec_context->pix_fmt = AV_PIX_FMT_YUV420P;

 if (strncmp("./video.mkv", out_file_path, 11) == 0) {
 printf("Writing .mkv...\n");
 codec_context->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
 codec_context->extradata = (uint8_t*)av_mallocz(1024 * 1024);
 codec_context->extradata_size = 1024 * 1024;
 } else {
 printf("Writing .mp4...\n");
 }

 // XXX avcodec_parameters_from_context is potentially superfluous (?)
 int ret = avcodec_parameters_from_context(video_stream->codecpar, codec_context);

 ret = avcodec_open2(codec_context, codec, NULL);

 avio_open(&format_context->pb, out_file_path, AVIO_FLAG_WRITE);

 ret = avformat_write_header(format_context, NULL);

 // create a black input frame
 AVFrame *input_frame = av_frame_alloc();
 input_frame->width = 1920;
 input_frame->height = 1080;
 input_frame->format = AV_PIX_FMT_YUV420P;
 ret = av_image_alloc(input_frame->data, input_frame->linesize, input_frame->width, input_frame->height, input_frame->format, 32);
 ptrdiff_t linesize[4] = { input_frame->linesize[0], input_frame->linesize[1], input_frame->linesize[2], input_frame->linesize[3] };
 ret = av_image_fill_black(input_frame->data, linesize, input_frame->format, 0, 1920, 1080);

 // write 2 seconds of video, all black
 for (size_t current_pts = 0; current_pts < 60; current_pts++) {
 input_frame->pts = av_rescale_q(current_pts, av_make_q(1, 30), codec_context->time_base);;

 ret = avcodec_send_frame(codec_context, input_frame);

 AVPacket* packet = av_packet_alloc();

 while (1) {
 ret = avcodec_receive_packet(codec_context, packet);
 if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
 break;
 } else if (ret < 0) {
 printf("avcodec_receive_packet failed");
 } else {
 av_packet_rescale_ts(packet, codec_context->time_base, video_stream->time_base);
 ret = av_interleaved_write_frame(format_context, packet);
 }
 }

 av_packet_free(&packet);
 }

 av_frame_free(&input_frame);

 // flush encoder
 avcodec_send_frame(codec_context, NULL);
 AVPacket *flush_packet = av_packet_alloc();
 while (avcodec_receive_packet(codec_context, flush_packet) != AVERROR_EOF) {
 //int ret = av_interleaved_write_frame(format_context_, packet);
 av_packet_rescale_ts(flush_packet, codec_context->time_base, video_stream->time_base);
 ret = av_write_frame(format_context, flush_packet);
 }
 av_packet_free(&flush_packet);

 ret = av_write_trailer(format_context);
 ret = avio_close(format_context->pb);

 return 0;
}


The error handling is stripped out, but it does not raise any errors.


This code works when I write into an mp4 file, but creates a corrupt file when writing into .mkv. You can change the output container format to mp4 by setting

char *out_file_path = "./video.mp4";

You can compile this by running


clang -I$(FFMPEG_DIR)/include -L$(FFMPEG_DIR)/lib -lavformat -lavcodec -lavutil main.c -o makemkv


The output I’m getting while the above code is running :


Writing .mkv...
[libx264 @ 0x139804c40] using cpu capabilities: ARMv8 NEON
[libx264 @ 0x139804c40] profile High, level 4.0, 4:2:0, 8-bit
[libx264 @ 0x139804c40] 264 - core 164 r3108 31e19f9 - H.264/MPEG-4 AVC codec - Copyleft 2003-2023 - http://www.videolan.org/x264.html - options: cabac=1 ref=1 deblock=1:0:0 analyse=0x3:0x3 me=dia subme=1 psy=1 psy_rd=1.00:0.00 mixed_ref=0 me_range=16 chroma_me=1 trellis=0 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=0 threads=15 lookahead_threads=2 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=3 b_pyramid=2 b_adapt=1 b_bias=0 direct=1 weightb=1 open_gop=0 weightp=1 keyint=250 keyint_min=25 scenecut=40 intra_refresh=0 rc=crf mbtree=0 crf=22.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 pb_ratio=1.30 aq=1:1.00


When I use the ffmpeg CLI, I can create a working .mkv from my working .mp4 like this :


ffmpeg -i video.mp4 -c:v copy created-with-ffmpeg-cli.mkv


I have uploaded the resulting video files here : https://drive.google.com/drive/folders/1FS-0fBAwKBbO-tyxC0VrFqcCyyqd0BR_?usp=sharing


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