<?php
namespace CompanyNameModuleNameControllerIndex;

use MagentoFrameworkAppActionAction;

class Test extends Action
{
    protected $videoGalleryProcessor;
    protected $_product;
    public function __construct(
        MagentoFrameworkAppActionContext $context,
        MagentoCatalogModelProduct $product,
        CompanyNameModuleNameModelProductGalleryVideoProcessor $videoGalleryProcessor
    ){
        parent::__construct($context);
        $this->_product = $product;
        $this->videoGalleryProcessor = $videoGalleryProcessor;
    }

    public function execute()
    {
        $productId = 1; // product id
        $product = $this->_product->load($productId);
        $product->setStoreId(0); //set store vise data

        // sample video data
        $videoData = [
            'video_id' => "abc", //set your video id
            'video_title' => "title", //set your video title
            'video_description' => "description", //set your video description
            'thumbnail' => "image path", //set your video thumbnail path.
            'video_provider' => "youtube",
            'video_metadata' => null,
            'video_url' => "https://www.youtube.com/watch?v=abc", //set your youtube video url
            'media_type' => MagentoProductVideoModelProductAttributeMediaExternalVideoEntryConverter::MEDIA_TYPE_CODE,
        ];

        //download thumbnail image and save locally under pub/media
        $videoData['file'] = $videoData['video_id'] . 'filename.jpg';

        // Add video to the product
        if ($product->hasGalleryAttribute()) {
            $this->videoGalleryProcessor->addVideo(
                $product,
                $videoData,
                ['image', 'small_image', 'thumbnail'],
                false,
                true
            );
        }
        $product->save();
    }
}

<?php
namespace CompanyNameModuleNameModelProductGalleryVideo;

use MagentoFrameworkExceptionLocalizedException;

class Processor extends MagentoCatalogModelProductGalleryProcessor
{
    /**
     * @var MagentoCatalogModelProductGalleryCreateHandler
     */
    protected $createHandler;

    /**
     * Processor constructor.
     * @param MagentoCatalogApiProductAttributeRepositoryInterface $attributeRepository
     * @param MagentoMediaStorageHelperFileStorageDatabase $fileStorageDb
     * @param MagentoCatalogModelProductMediaConfig $mediaConfig
     * @param MagentoFrameworkFilesystem $filesystem
     * @param MagentoCatalogModelResourceModelProductGallery $resourceModel
     * @param MagentoCatalogModelProductGalleryCreateHandler $createHandler
     */
    public function __construct(
        MagentoCatalogApiProductAttributeRepositoryInterface $attributeRepository,
        MagentoMediaStorageHelperFileStorageDatabase $fileStorageDb,
        MagentoCatalogModelProductMediaConfig $mediaConfig,
        MagentoFrameworkFilesystem $filesystem,
        MagentoCatalogModelResourceModelProductGallery $resourceModel,
        MagentoCatalogModelProductGalleryCreateHandler $createHandler
    )
    {
        parent::__construct($attributeRepository, $fileStorageDb, $mediaConfig, $filesystem, $resourceModel);
        $this->createHandler = $createHandler;
    }

    /**
     * @param MagentoCatalogModelProduct $product
     * @param array $videoData
     * @param array $mediaAttribute
     * @param bool $move
     * @param bool $exclude
     * @return string
     * @throws LocalizedException
     */
    public function addVideo(
        MagentoCatalogModelProduct $product,
        array $videoData,
        $mediaAttribute = null,
        $move = false,
        $exclude = true
    ) {
        $file = $this->mediaDirectory->getRelativePath($videoData['file']);

        if (!$this->mediaDirectory->isFile($file)) {
            throw new LocalizedException(__('The image does not exist.'));
        }

        $pathinfo = pathinfo($file);
        $imgExtensions = ['jpg', 'jpeg', 'gif', 'png'];
        if (!isset($pathinfo['extension']) || !in_array(strtolower($pathinfo['extension']), $imgExtensions)) {
            throw new LocalizedException(__('Please correct the image file type.'));
        }

        $fileName = MagentoMediaStorageModelFileUploader::getCorrectFileName($pathinfo['basename']);
        $dispretionPath = MagentoMediaStorageModelFileUploader::getDispretionPath($fileName);
        $fileName = $dispretionPath . '/' . $fileName;

        $fileName = $this->getNotDuplicatedFilename($fileName, $dispretionPath);

        $destinationFile = $this->mediaConfig->getTmpMediaPath($fileName);

        try {
            /** @var $storageHelper MagentoMediaStorageHelperFileStorageDatabase */
            $storageHelper = $this->fileStorageDb;
            if ($move) {
                $this->mediaDirectory->renameFile($file, $destinationFile);

                //Here, filesystem should be configured properly
                $storageHelper->saveFile($this->mediaConfig->getTmpMediaShortUrl($fileName));
            } else {
                $this->mediaDirectory->copyFile($file, $destinationFile);

                $storageHelper->saveFile($this->mediaConfig->getTmpMediaShortUrl($fileName));
            }
        } catch (Exception $e) {
            throw new LocalizedException(__('We couldn't move this file: %1.', $e->getMessage()));
        }

        $fileName = str_replace('\', '/', $fileName);

        $attrCode = $this->getAttribute()->getAttributeCode();
        $mediaGalleryData = $product->getData($attrCode);
        $position = 0;
        if (!is_array($mediaGalleryData)) {
            $mediaGalleryData = ['images' => []];
        }

        foreach ($mediaGalleryData['images'] as &$image) {
            if (isset($image['position']) && $image['position'] > $position) {
                $position = $image['position'];
            }
        }

        $position++;

        unset($videoData['file']);
        $mediaGalleryData['images'][] = array_merge([
            'file' => $fileName,
            'label' => $videoData['video_title'],
            'position' => $position,
            'disabled' => (int)$exclude
        ], $videoData);

        $product->setData($attrCode, $mediaGalleryData);

        if ($mediaAttribute !== null) {
            $product->setMediaAttribute($product, $mediaAttribute, $fileName);
        }

        $this->createHandler->execute($product);

        return $fileName;
    }
}

<?php
    $_helper = $this->helper('MagentoCatalogHelperOutput');
    $objectManager = MagentoFrameworkAppObjectManager::getInstance();
    $_product = $objectManager->get('MagentoFrameworkRegistry')->registry('current_product');//get current product
?>

<?php if($proVideo = $_helper->productAttribute($_product,$_product->getVideoName(), 'video_name')):?>
    <?php $videoUrl = $this->getUrl('pub/media/catalog/product/videos/').$proVideo; ?>
    <div class="prod_video_bg">
        <video width="400" controls>
          <source src="<?php echo $videoUrl; ?>" type="video/mp4">
        </video>
    </div>
<?php endif; ?>