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• avcodec/dvbsubdec : Check object position

  5 mars 2019, par Michael Niedermayer

  avcodec/dvbsubdec : Check object position
  Reference : ETSI EN 300 743 V1.2.1  7.2.2 Region composition segment
  Fixes : Timeout
  
  Fixes : 13325/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_DVBSUB_fuzzer-5143979392237568
  Found-by : continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
  
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavcodec/dvbsubdec.c

• Separate simultaneously changing regions of video into individual videos

  17 juillet 2019, par Elle Fie

  Given a single video stream (up to 4K resolution), where only small displayed portions may change, I’d like to identify these changing sections and create separate video streams, one for each changing section of the input video stream, in real time.

  Note that this is spatial extraction, not time slicing !

  Q1 : Is there a better name to address this process ?

  Q2 : Is this an already solved problem ?

  It seems ImageMagick’s Compare program supports diffing two images, which I can process to identify regions as coordinates for an ffmpeg crop (launched in parallel for each discovered diff region), but this method relies on having a PNG stream to avoid false positive diffs due to lossy encoding. Also, too slow to happen in real time.

  Q3 : Is there any way ffmpeg can dump out the causal regions influencing scene-change detection ?

• how to download portion of video which was uploaded into AWS s3 bucket, though Nodejs SDKs

  22 février 2024, par rama rangeswara reddy

  I have uploaded a 1GB .mp4 file to an AWS S3 bucket. Using the AWS-SDK provided by the npm package, I am able to download the entire video. However, I have a specific requirement to generate a thumbnail at the 6-second mark of the video. Currently, I download the entire 1GB video to my local machine and then generate the thumbnail at the desired duration.

  


  To optimize server resources and reduce disk load, I plan to download only the first 10 seconds of the video, which should be approximately 10MB or less in size. By doing so, I can significantly reduce download time and server load while still fulfilling my requirement of generating the thumbnail at the 6-second mark. Therefore, instead of downloading the entire 1GB video, I aim to download only the 10MB segment corresponding to the first 10 seconds of the video.

  


  I am using nodejs, expressJS, as backed Technologies.

  


  `

  


  `async function downloadS3FileToLocalDirAndReturnPath(videoKey) {
    return new Promise(async (resolve, reject) => {
        try {
            AWS.config.update({
                accessKeyId: config.AWS.KEYS.accessKeyId,
                secretAccessKey: config.AWS.KEYS.secretAccessKey,
                region: config.AWS.KEYS.region,
                httpOptions: config.AWS.KEYS.httpOptions
            });
            const s3 = new AWS.S3();

            // Specify the local file path where you want to save the downloaded video
            const localFilePath = `${os.tmpdir()}/${Date.now()}_sre.mp4`;

            // Configure the parameters for the S3 getObject operation
            const params = {
                Bucket: config.AWS.S3_BUCKET,
                Key: videoKey
            };

            const result = await s3.getObject(params).promise();
            const fileContent = result.Body;
            fs.writeFileSync(localFilePath, fileContent);
            resolve(localFilePath);
        } catch (error) {
            reject(error);
        }
    });
}`


  


  this code was working fine to download the whole video , but i need to download only first 10 seconds duration

  


  S3 : How to do a partial read / seek without downloading the complete file ?

  


  I tried this ,before posting this question with above post, video was downloading , it was not playing , by throwing this error , the file contains no playable streams

  


  async function generateThumbnails(videoKey) {

const s3 = new AWS.S3();

const params = {
    Bucket: KEYS.bucket,
    Key: videoKey, // Specify the key of the video file in S3
    Range: `bytes=0-${1024 * 800}`, // Specify the range of bytes you want to retrieve
};

const file = fs.createWriteStream(`/tmp/${Date.now()}_rama.mp4`);

const s3Stream = s3.getObject(params).createReadStream();

s3Stream.pipe(file);

s3Stream.on("error", (error) => {
    console.log("Error Occured while File downloading!! ");
});

s3Stream.on("finish", () => {
    console.log("File downloaded Successfully ");
});


  


  }