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Autres articles (102)
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Multilang : améliorer l’interface pour les blocs multilingues
18 février 2011, parMultilang est un plugin supplémentaire qui n’est pas activé par défaut lors de l’initialisation de MediaSPIP.
Après son activation, une préconfiguration est mise en place automatiquement par MediaSPIP init permettant à la nouvelle fonctionnalité d’être automatiquement opérationnelle. Il n’est donc pas obligatoire de passer par une étape de configuration pour cela. -
L’agrémenter visuellement
10 avril 2011MediaSPIP est basé sur un système de thèmes et de squelettes. Les squelettes définissent le placement des informations dans la page, définissant un usage spécifique de la plateforme, et les thèmes l’habillage graphique général.
Chacun peut proposer un nouveau thème graphique ou un squelette et le mettre à disposition de la communauté. -
Possibilité de déploiement en ferme
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Cela permet, par exemple : de pouvoir partager les frais de mise en œuvre entre plusieurs projets / individus ; de pouvoir déployer rapidement une multitude de sites uniques ; d’éviter d’avoir à mettre l’ensemble des créations dans un fourre-tout numérique comme c’est le cas pour les grandes plate-formes tout public disséminées sur le (...)
Sur d’autres sites (8016)
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How do I use the FFmpeg libraries to extract every nth frame from a video and save it as a small image file in C++ ?
1er novembre 2022, par PanchsAfter experimenting with the examples on the FFmpeg documentation, I was finally able to create a short program that extracts every nth frame from a video. However, the output files that it produces are huge at over 15mb for each image. How can I change this to produce lower quality images ?


The result I am trying to get is done easily on the command line with :


ffmpeg -i [input video] -vf "select=not(mod(n\,10))" -fps_mode vfr img_%03d.jpg

For a video with about 500 frames, this creates 50 images that are only about 800kb each ; how am would I be able to mimic this in my program ?


My code consists of opening the input file, decoding the packets, then saving the frames :


#include <cstdio>
#include <cstdlib>
#include <iostream>

extern "C" {
#include <libavcodec></libavcodec>avcodec.h>
#include <libavformat></libavformat>avformat.h>
#include <libavfilter></libavfilter>buffersink.h>
#include <libavfilter></libavfilter>buffersrc.h>
#include <libavutil></libavutil>opt.h>
#include <libswscale></libswscale>swscale.h>
}

static AVFormatContext *fmt_ctx;
static AVCodecContext *dec_ctx;
static int video_stream_index = -1;

// OPEN THE INPUT FILE
static int open_input_file(const char *filename) {
 // INIT VARS AND FFMPEG OBJECTS
 int ret;
 const AVCodec *dec;

 // OPEN INPUT FILE
 if((ret = avformat_open_input(&fmt_ctx, filename, NULL, NULL)) < 0) {
 printf("ERROR: failed to open input file\n");
 return ret;
 }

 // FIND STREAM INFO BASED ON INPUT FILE
 if((ret = avformat_find_stream_info(fmt_ctx, NULL)) < 0) {
 printf("ERROR: failed to find stream information\n");
 return ret;
 }

 // FIND THE BEST VIDEO STREAM FOR THE INPUT FILE
 ret = av_find_best_stream(fmt_ctx, AVMEDIA_TYPE_VIDEO, -1, -1, &dec, 0);
 if(ret < 0) {
 printf("ERROR: failed to find a video stream in the input file\n");
 return ret;
 }
 video_stream_index = ret;

 // ALLOCATE THE DECODING CONTEXT FOR THE INPUT FILE
 dec_ctx = avcodec_alloc_context3(dec);
 if(!dec_ctx) {
 printf("ERROR: failed to allocate decoding context\n");
 // CAN NOT ALLOCATE MEMORY ERROR
 return AVERROR(ENOMEM);
 }
 avcodec_parameters_to_context(dec_ctx, fmt_ctx->streams[video_stream_index]->codecpar);

 // INIT THE VIDEO DECODER
 if((ret = avcodec_open2(dec_ctx, dec, NULL)) < 0) {
 printf("ERROR: failed to open video decoder\n");
 return ret;
 }

 return 0;
}

// SAVE THE FILE
static void save(unsigned char *buf, int wrap, int x_size, int y_size, char *file_name) {
 // INIT THE EMPTY FILE
 FILE *file;

 // OPEN AND WRITE THE IMAGE FILE
 file = fopen(file_name, "wb");
 fprintf(file, "P6\n%d %d\n%d\n", x_size, y_size, 255);
 for(int i = 0; i < y_size; i++) {
 fwrite(buf + i * wrap, 1, x_size * 3, file);
 }
 fclose(file);
}

// DECODE FRAME AND CONVERT IT TO AN RGB IMAGE
static void decode(AVCodecContext *cxt, AVFrame *frame, AVPacket *pkt,
 const char *out_file_name, const char *file_ext, int mod=1) {
 // INIT A BLANK CHAR TO HOLD THE FILE NAME AND AN EMPTY INT TO HOLD FUNCTION RETURN VALUES
 char buf[1024];
 int ret;

 // SEND PACKET TO DECODER
 ret = avcodec_send_packet(cxt, pkt);
 if(ret < 0) {
 printf("ERROR: error sending packet for decoding\n");
 exit(1);
 }

 // CREATE A SCALAR CONTEXT FOR CONVERSION
 SwsContext *sws_ctx = sws_getContext(dec_ctx->width, dec_ctx->height, dec_ctx->pix_fmt, dec_ctx->width,
 dec_ctx->height, AV_PIX_FMT_RGB24, SWS_BICUBIC, NULL, NULL, NULL);

 // CREATE A NEW RGB FRAME FOR CONVERSION
 AVFrame* rgb_frame = av_frame_alloc();
 rgb_frame->format = AV_PIX_FMT_RGB24;
 rgb_frame->width = dec_ctx->width;
 rgb_frame->height = dec_ctx->height;

 // ALLOCATE A NEW BUFFER FOR THE RGB CONVERSION FRAME
 av_frame_get_buffer(rgb_frame, 0);

 // WHILE RETURN COMES BACK OKAY (FUNCTION RETURNS >= 0)...
 while(ret >= 0) {
 // GET FRAME BACK FROM DECODER
 ret = avcodec_receive_frame(cxt, frame);
 // IF "RESOURCE TEMP NOT AVAILABLE" OR "END OF FILE" ERROR...
 if(ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
 return;
 } else if(ret < 0) {
 printf("ERROR: error during decoding\n");
 exit(1);
 }

 // IF FRAME NUMBER IF THE (MOD)TH FRAME...
 if(cxt->frame_number % mod == 0){
 // OUTPUT WHICH FRAME IS BEING SAVED
 printf("saving frame %03d\n", cxt->frame_number);
 // REMOVES TEMPORARY BUFFERED DATA
 fflush(stdout);

 // SCALE (CONVERT) THE OLD FRAME TO THE NEW RGB FRAME
 sws_scale(sws_ctx, frame->data, frame->linesize, 0, frame->height,
 rgb_frame->data, rgb_frame->linesize);

 // SET "BUF" TO THE OUTPUT FILE PATH (SAVES TO "out_file_name_###.file_ext")
 snprintf(buf, sizeof(buf), "%s_%03d.%s", out_file_name, cxt->frame_number, file_ext);
 // SAVE THE FRAME
 save(rgb_frame->data[0], rgb_frame->linesize[0], rgb_frame->width, rgb_frame->height, buf);
 }
 }
}

int main() {
 // SIMULATE COMMAND LINE ARGUMENTS
 char argv0[] = "test";
 char argv1[] = "/User/Desktop/frames/test_video.mov";
 char *argv[] = {argv0, argv1, nullptr};

 // INIT VARS AND FFMPEG OBJECTS
 int ret;
 AVPacket *packet;
 AVFrame *frame;

 // ALLOCATE FRAME AND PACKET
 frame = av_frame_alloc();
 packet = av_packet_alloc();
 if (!frame || !packet) {
 fprintf(stderr, "Could not allocate frame or packet\n");
 exit(1);
 }

 // IF FILE DOESN'T OPEN, GO TO THE END
 if((ret = open_input_file(argv[1])) < 0) {
 goto end;
 }
 
 // READ ALL THE PACKETS - simple
 while(av_read_frame(fmt_ctx, packet) >= 0) {
 // IF PACKET INDEX MATCHES VIDEO INDEX...
 if (packet->stream_index == video_stream_index) {
 // SEND PACKET TO THE DECODER and SAVE
 std::string name = "/User/Desktop/frames/img";
 std::string ext = "bmp";
 decode(dec_ctx, frame, packet, name.c_str(), ext.c_str(), 5);
 }

 // UNREFERENCE THE PACKET
 av_packet_unref(packet);
 }

 // END MARKER
 end:
 avcodec_free_context(&dec_ctx);
 avformat_close_input(&fmt_ctx);
 av_frame_free(&frame);
 av_packet_free(&packet);

 // FINAL ERROR CATCH
 if (ret < 0 && ret != AVERROR_EOF) {
 fprintf(stderr, "Error occurred: %s\n", av_err2str(ret));
 exit(1);
 }

 exit(0);
}
</iostream></cstdlib></cstdio>

I am not sure how to go about producing images that are much smaller in size like the ones produced on the command line. I have a feeling that this is possible somehow during the conversion to RGB or the saving of the file but I can't seem to figure out how.


Also, is there any way that I could go about this much more efficiently ? On the command line, this finishes very quickly (no more than a second or two for a 9 sec. movie at 60 fps).


-
Flutter FFmpeg | Concat Multiple Videos From TXT File And Save As A Video
7 mai 2023, par Muhammad HassanI have a text file with all path of video files that I want to concat using
https://pub.dev/packages/ffmpeg_kit_flutter in my flutter app.


For this purpose, I write a file
my_file.txtwith the below data...

/data/user/0/com.example.video_merger/cache/75f72300-1203-4e2c-93cf-65777152f1d16524788775537818173.mp4
/data/user/0/com.example.video_merger/cache/318d5ea7-3e0c-4453-903b-06966aa86f348487775694692938421.mp4


Now I am using the below code to merge all the upper videos.


String outputPath = "/data/user/0/com.example.video_merger/app_flutter/output.mp4";
String commandToExecute = '-f concat -i $rawDocumentPath/my_file.txt -c copy $outputPath';
FFmpegKit.execute(commandToExecute).then((session) async {
 final returnCode = await session.getReturnCode();
 print("FFmpeg Process Exited With ReturnCode = $returnCode");
 GallerySaver.saveVideo(outputPath).then((_) {
 print("Merged Video Saved");
 });
 if (ReturnCode.isSuccess(returnCode)) {
 // SUCCESS
 } else if (ReturnCode.isCancel(returnCode)) {
 // CANCEL
 } else {
 // ERROR
 }
});


But it is giving me error as shown below...


FFmpeg Process Exited With ReturnCode = 1 
E/GallerySaver(31493): /data/user/0/com.example.video_merger/app_flutter/output.mp4: open failed: ENOENT (No such file or directory)


But when I use the below
ffmpegcommand directly without reading from text file works fine and save my video.

String commandToExecute = '-y -i ${_storedVideoOne!.path} -i ${_storedVideoTwo!.path} -r 24000/1001 -filter_complex \'[0:v:0][0:a:0][1:v:0][1:a:0]concat=n=2:v=1:a=1[out]\' -map \'[out]\' $outputPath';


Now my question is that I will have dynamic number of videos to concat so I want to use text file where I will write all paths then will make merged video from them. So what is the error in my
ffmpegcommand...???

Log Report :


I used the log reporting as follows to get the below output of errors...


FFmpegKit.executeAsync(
 commandToExecute2,
 (session) async {
 final returnCode = await session.getReturnCode();
 print("FFmpeg Process Exited With ReturnCode = $returnCode");
 GallerySaver.saveVideo(outputPath).then((_) async {
 print("Merged Video Saved");
 });
 if (ReturnCode.isSuccess(returnCode)) {
 // SUCCESS
 } else if (ReturnCode.isCancel(returnCode)) {
 // CANCEL
 } else {
 // ERROR
 }
 },
 (log) {
 print("XXXXXXXXXXXX fFmpeg XXXXXXXXXX ${log.getMessage()}");
 },
 );


And here is the Log Output...


I/flutter ( 5432): Text On File: /data/user/0/com.example.video_merger/cache/75f72300-1203-4e2c-93cf-65777152f1d16524788775537818173.mp4
I/flutter ( 5432): /data/user/0/com.example.video_merger/cache/318d5ea7-3e0c-4453-903b-06966aa86f348487775694692938421.mp4
I/flutter ( 5432): XXXXXXXXXXXX fFmpeg XXXXXXXXXX ffmpeg version n5.1.2
I/flutter ( 5432): XXXXXXXXXXXX fFmpeg XXXXXXXXXX Copyright (c) 2000-2022 the FFmpeg developers
I/flutter ( 5432): XXXXXXXXXXXX fFmpeg XXXXXXXXXX
I/flutter ( 5432): XXXXXXXXXXXX fFmpeg XXXXXXXXXX built with Android (7155654, based on r399163b1) clang version 11.0.5 (https://android.googlesource.com/toolchain/llvm-project 87f1315dfbea7c137aa2e6d362dbb457e388158d)
I/flutter ( 5432): XXXXXXXXXXXX fFmpeg XXXXXXXXXX configuration: --cross-prefix=aarch64-linux-android- --sysroot=/files/android-sdk/ndk/22.1.7171670/toolchains/llvm/prebuilt/linux-x86_64/sysroot --prefix=/home/taner/Projects/ffmpeg-kit/prebuilt/android-arm64/ffmpeg --pkg-config=/usr/bin/pkg-config --enable-version3 --arch=aarch64 --cpu=armv8-a --target-os=android --enable-neon --enable-asm --enable-inline-asm --ar=aarch64-linux-android-ar --cc=aarch64-linux-android24-clang --cxx=aarch64-linux-android24-clang++ --ranlib=aarch64-linux-android-ranlib --strip=aarch64-linux-android-strip --nm=aarch64-linux-android-nm --extra-libs='-L/home/taner/Projects/ffmpeg-kit/prebuilt/android-arm64/cpu-features/lib -lndk_compat' --disable-autodetect --enable-cross-compile --enable-pic --enable-jni --enable-optimizations --enable-swscale --disable-static --enable-shared --enable-pthreads --enable-v4l2-m2m --disable-outdev=fbdev --disable-indev=fbdev --enable-small --disable-xmm-clobber-test --disable-debug --enable-lto --disable-neon-clobber-t
I/flutter ( 5432): XXXXXXXXXXXX fFmpeg XXXXXXXXXX libavutil 57. 28.100 / 57. 28.100
I/flutter ( 5432): XXXXXXXXXXXX fFmpeg XXXXXXXXXX libavcodec 59. 37.100 / 59. 37.100
I/flutter ( 5432): XXXXXXXXXXXX fFmpeg XXXXXXXXXX libavformat 59. 27.100 / 59. 27.100
I/flutter ( 5432): XXXXXXXXXXXX fFmpeg XXXXXXXXXX libavdevice 59. 7.100 / 59. 7.100
I/flutter ( 5432): XXXXXXXXXXXX fFmpeg XXXXXXXXXX libavfilter 8. 44.100 / 8. 44.100
I/flutter ( 5432): XXXXXXXXXXXX fFmpeg XXXXXXXXXX libswscale 6. 7.100 / 6. 7.100
I/flutter ( 5432): XXXXXXXXXXXX fFmpeg XXXXXXXXXX libswresample 4. 7.100 / 4. 7.100
I/flutter ( 5432): XXXXXXXXXXXX fFmpeg XXXXXXXXXX [concat @ 0xb400007d62447910] Line 1: unknown keyword '/data/user/0/com.example.video_merger/cache/75f72300-1203-4e2c-93cf-65777152f1d16524788775537818173.mp4'
I/flutter ( 5432): XXXXXXXXXXXX fFmpeg XXXXXXXXXX /data/user/0/com.example.video_merger/app_flutter/my_file.txt: Invalid data found when processing input
I/flutter ( 5432): FFmpeg Process Exited With ReturnCode = 1


-
FFmpeg does not save the mp4 clips to file
31 janvier 2021, par oo92I'm using the FFmpeg Python library to save 60-second mp4 clips to a .mp4 file from Twitch live streams using its API. This is my code :


current_dir = os.getcwd()

client = TwitchClient(client_id='')
streams_now = client.streams.get_live_streams(limit=100, offset=900)
epoch = str(math.ceil(time.time()))

if not os.path.exists(current_dir + '/twitch_videos/'):
 os.mkdir(current_dir + '/twitch_videos/')

for i in range(0, 100):
 try:
 username = streams_now[i]['channel']['name']
 id = streams_now[i]['id']
 game = streams_now[i]['game']
 game = game.translate(str.maketrans({':': '-', ' ': '-', "'": '', '!': '', '&': '_', '.': '', '+': '_'}))
 streaming = streamlink.streams('http://twitch.tv/' + username)
 stream = streaming["best"].url

 twitch_stream = ffmpeg.input(stream)

 twitch_stream = ffmpeg.filter(twitch_stream,
 'fps',
 fps=1,
 round='up')

 twitch_stream = ffmpeg.output(twitch_stream,
 current_dir + '/twitch_videos/' + '%d_' + username + '_' + epoch + '.mp4',
 sc_threshold='0',
 g='60',
 f='segment',
 segment_time='600',
 segment_format_options='movflags=+faststart',
 reset_timestamps='1')frl3dqgn21bbpp6tajjvg5pdevczac
 ffmpeg.run(twitch_stream)


 except:
 pass


I am concatenating the path it should go to the name of the file but the folder is empty after I take a look. The reason why its in the try-catch block is because some streams do not have the
besttag so I want to skip those.

Update


I put a bunch of print statements inside the try block and none of them get printed. I put similar if statements inside the except block and they are all printed. This means that there is something wrong with my code inside the try block. This tells me that the code inside the try block never gets executed.


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