Stuttering at beginning of rendered video

In the rendered video, there is stuttering in the first ~0.5 seconds that is not present in the original video.

Render ID (staging): 8502941f-d8ea-4675-89c1-ef347feaba0a

Original video: master (7).mp4 - Google Drive
Rendered video:
high (5).mp4 - Google Drive

Hey @walkthreads,

How did you originally add the audio to the video?

I’m asking as video editors often run into problems when dealing with variable bit rate audio.

We’re using the MediaRecorder API in the browser to record the user’s webcam and microphone in the browser. I believe this does default to variable bitrate audio. It looks like constant bitrate audio is not well supported in the API yet. Are there any workarounds here?

Ok that is likely to cause the issue.

We are working on an ingestion service. This service will be designed to fix issues such as these. This is still a couple of months away however.

Until that time you have two options:

  1. Add the audio to the clip separately using the audio clip
  2. Convert the video file to ensure the audio bitrate is more constant

1. Add the audio to the clip separately using the audio asset

You can use the audio asset to overlay audio on your video, and set the video volume property to 0.

You mentioned you are recording both the webcam and audio from the browser so this may not be the best option if it results in syncing issues.

2. Convert the video file to ensure the audio bitrate is more constant

I used the following ffmpeg command to keep the audio bitrate constant:

ffmpeg -i master.mp4 -ab 124k master-new.mp4

This resulted in the following video (without the glitch):

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I went back through some of our videos and it looks like this issue started happening for us on 2022/2/1. Did something change on Shotstack’s end around this time?

We update our edit engine very regularly. It may be possible that an update could have had an impact.

As different ways of encoding videos can have different impacts on the output quality we always recommend to keep the video assets ingested as free as possible from optimisations meant to make streaming more efficient (such as variable bit rates).

The fact that we see a growing proportion of ingested video already optimised for streaming and not editing is another reason for the upcoming ingestion service. This way we will allow assets to be standardised and make it easier to edit videos with different type of encodings and optimisations.

FYI this issue seems fixed for us, wondering if any specific changes were made on Shotstack’s end to do so?

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Yes. We introduced a fix yesterday. I’m glad to hear it’s resolved the issue for you.

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