Using FFmpeg with Serverless function.

I am facing difficulty with serverless function to creating video and upload it to digital occan spaces. The ffmpeg gives me error while generating the video. here is my generating and uploading process:

const { PassThrough } = require("stream");
const passThroughStream = **new** PassThrough();
              const buffers = [];

              passThroughStream.on('data', (chunk) => buffers.push(chunk));
              passThroughStream.on('end', async () => {
                const buffer = Buffer.concat(buffers);
                const contentLength = buffer.length;

                try {
                  const url = await uploadFile(userId, buffer, videoPath, contentLength);
                  resolve({ url, duration });
                } catch (uploadError) {
                  reject(uploadError);
                }
              });

              ffmpeg()
                .input(svgPaths[index][dim])
                .loop(
                  index === audioMappings.length - 1 ? duration + 2.7 : duration
                )
                .input(audioFilePath)
                .audioCodec("aac")
                .videoCodec("libx264")
                .videoBitrate(950)
                .format("mp4")
                .fps(25)
                .size(dim)
                .output(passThroughStream)
                .on('start', (commandLine) => {
                  console.log('Spawned Ffmpeg with command:', commandLine);
                })
                .on('stderr', (stderrLine) => {
                  console.log('Stderr output:', stderrLine);
                })
                .on('error', (err, stdout, stderr) => {
                  const errorResponse = { error: "ffmpeg error", details: err.message, stdout, stderr };
                  reject(errorResponse);
                })
                .on('end', () => {
                  console.log(`ffmpeg processing complete for index ${index} and dimension ${dim}`);
                })
                .run();
            });
          });

          outputVideoPaths.push(result.url);