회원 동영상 업로드 -> YouTube API 이용하여 채널에 업로드 하면 가능할거 같습니다.

참고 1 : https://kminito.tistory.com/5#google_vignette

참고 2 : PHP 이용시

composer require google/apiclient

<?php

require_once 'vendor/autoload.php';

function getClient()
{
    $client = new Google_Client();
    $client->setApplicationName("YouTube Upload App");
    $client->setScopes([
        'https://www.googleapis.com/auth/youtube.upload',
        'https://www.googleapis.com/auth/youtube'
    ]);
    $client->setAuthConfig('path/to/your/client_secret.json');
    $client->setAccessType('offline');

    // Load previously authorized credentials from a file.
    $credentialsPath = 'path/to/your/credentials.json';
    if (file_exists($credentialsPath)) {
        $accessToken = json_decode(file_get_contents($credentialsPath), true);
        $client->setAccessToken($accessToken);
    }

    // If there is no previous token or it's expired.
    if ($client->isAccessTokenExpired()) {
        // Refresh the token if possible, else fetch a new one.
        if ($client->getRefreshToken()) {
            $client->fetchAccessTokenWithRefreshToken($client->getRefreshToken());
        } else {
            // Request authorization from the user.
            $authUrl = $client->createAuthUrl();
            printf("Open the following link in your browser:\n%s\n", $authUrl);
            print 'Enter verification code: ';
            $authCode = trim(fgets(STDIN));

            // Exchange authorization code for an access token.
            $accessToken = $client->fetchAccessTokenWithAuthCode($authCode);
            $client->setAccessToken($accessToken);

            // Save the token to a file.
            if (!file_exists(dirname($credentialsPath))) {
                mkdir(dirname($credentialsPath), 0700, true);
            }
            file_put_contents($credentialsPath, json_encode($client->getAccessToken()));
        }
    }
    return $client;
}

function uploadVideo($videoPath, $title, $description, $tags, $category = 22)
{
    try {
        $client = getClient();
        $youtube = new Google_Service_YouTube($client);

        $snippet = new Google_Service_YouTube_VideoSnippet();
        $snippet->setTitle($title);
        $snippet->setDescription($description);
        $snippet->setTags($tags);
        $snippet->setCategoryId($category);

        $status = new Google_Service_YouTube_VideoStatus();
        $status->setPrivacyStatus("private"); // or "public" or "unlisted"

        $video = new Google_Service_YouTube_Video();
        $video->setSnippet($snippet);
        $video->setStatus($status);

        $chunkSizeBytes = 1 * 1024 * 1024;

        $client->setDefer(true);
        $insertRequest = $youtube->videos->insert("status,snippet", $video);
        $media = new Google_Http_MediaFileUpload(
            $client,
            $insertRequest,
            'video/*',
            null,
            true,
            $chunkSizeBytes
        );
        $media->setFileSize(filesize($videoPath));

        $status = false;
        $handle = fopen($videoPath, "rb");
        while (!$status && !feof($handle)) {
            $chunk = fread($handle, $chunkSizeBytes);
            $status = $media->nextChunk($chunk);
        }
        fclose($handle);

        $client->setDefer(false);

        if ($status) {
            echo "Video uploaded successfully. Video ID: " . $status['id'];
        }

        return $status;
    } catch (Google_Service_Exception $e) {
        echo "An error occurred: " . $e->getMessage();
    } catch (Google_Exception $e) {
        echo "An error occurred: " . $e->getMessage();
    }
}

// 사용 예시
$videoPath = 'path/to/your/video.mp4';
$title = '업로드 테스트 동영상';
$description = '이 동영상은 API를 통해 업로드되었습니다.';
$tags = ['테스트', 'API', '업로드'];

uploadVideo($videoPath, $title, $description, $tags);