API doesn't actually work with floats, just integers

Shotstack API
1

So I’ve spent more than a day trying to sort out why ~5 seconds of nothing kept getting added on to all of my successful renders despite exact time specifications (e.g. "length": 8.152000000003582).

Early on I thought that perhaps it’s due to the specificity of the number, because I wasn’t flooring or rounding the fractional portion of the lengths and starting positions, but then I looked at the API documentation and it insisted that floats are exactly what I should be using. There were only integer examples in the documentation but I assumed that was just for simplicity since it says to specify a float and not an integer everywhere I looked.

All elements of the video had ended by the exact length expected, but the video just had another five seconds of nothing. I noticed the clips were finishing at lengths shorter than expected in many cases but it was hard to tell for about 25-50% of the video but it was eventually off by some part of the specified length and video ended early.

After all of this it became pretty clear that the videos weren’t going to play for the proper amount of time if I didn’t specify their start times and lengths as integers so I changed my code to supply integers instead. Not only did this fix the play time of the clips to actually be correct but it also got rid of the ~5 seconds of black at the end of the video (after everything had ended).

So, first of all, I think you ought to either fix this or change your documentation to specify that you require integers for time values. Second, I’d really like to know how clips playing for less time than specified would lead to a longer runtime. It would make more sense if the clips just ended before the audio (since both audio tracks play on top of each other and have a very clear endpoint of the video’s end), or even if the video itself ended earlier (even though that would also be odd), but why does it produce a longer render?

I’m glad I got it working but it bugs me when troubleshooting only produces a fix and no answers. I like to know. :stuck_out_tongue:

2

The API does support floats, but is fixed to the FPS used. For example. If you use a duration of 10.1 seconds at 25fps that would lead to a video with 252.5 frames. That would be cut to 252 frames or 10.08 seconds.

Could you share the JSON where floats are not working for you? I would love to see what may be happening.

3

That definitely makes sense, in regards to the duration of each clip getting cut short. The excess time at the end is still a mystery, though. I think I saved the old JSON but I know how to reproduce it if not. I’ll report back shortly.

4

Found one! This should produce the ~5 second excess of empty black video at the end.

/* RENDER ID: c75d52b9-b680-4bca-8389-522bd4ed74e7 */
{
    "timeline": {
        "background": "#000000",
        "fonts": [
            {
                "src": "https:\/\/shotstack-assets.s3-ap-southeast-2.amazonaws.com\/fonts\/OpenSans-Regular.ttf"
            }
        ],
        "tracks": [
            {
                "clips": [
                    {
                        "asset": {
                            "type": "audio",
                            "src": "https:\/\/dl.airtable.com\/.attachments\/5a024bf46693166fc771ec20118a4341\/600920d5\/FILMPAC_Buckshot_FMAAA1539.mp3?ts=1653429025&userId=usrQ4kJRtjzTLK4bl&cs=3ef57426b2ccf60f",
                            "volume": 0.1
                        },
                        "start": 0,
                        "length": 100.58200000000221,
                        "fit": "crop",
                        "position": "center",
                        "transition": {
                            "out": "fade"
                        },
                        "opacity": 1
                    },
                    {
                        "asset": {
                            "type": "html",
                            "html": "<h1>Weaponize Your Garbage Disposal to Stop Would Be Intruders<\/h1><p>by Globot Baseball Sanderpiel<\/p>",
                            "css": "h1 { color: #ffffff; font-size: 32px; font-family: \"Open Sans\"; margin-left: 48px; margin-bottom: 4px; width: 1400px; line-height: 100%; } p { font-size: 18px; color: #ffffff; text-transform: uppercase; font-family: \"Open Sans\"; margin-left: 48px; width: 1400px; }",
                            "width": 1400,
                            "height": 160,
                            "background": "transparent",
                            "position": "left"
                        },
                        "start": 5,
                        "length": 95.58200000000221,
                        "fit": "none",
                        "position": "bottomLeft",
                        "offset": {
                            "x": 0,
                            "y": 0
                        },
                        "transition": {
                            "out": "fade"
                        },
                        "opacity": 1
                    }
                ]
            },
            {
                "clips": [
                    {
                        "asset": {
                            "type": "audio",
                            "src": "https:\/\/dl.airtable.com\/.attachments\/0eb71a52a855bc4c421ea9eefe6f9830\/39c77f86\/03f9d09262887737464b8e100416d352.mp3?ts=1653429006&userId=usrQ4kJRtjzTLK4bl&cs=1c7cb38273aec8ba",
                            "volume": 1
                        },
                        "start": 5.25,
                        "length": 95.58200000000221,
                        "fit": "crop",
                        "position": "center",
                        "opacity": 1
                    },
                    {
                        "asset": {
                            "type": "image",
                            "src": "https:\/\/entropi.ca\/alh\/aLh-Watermark-bg-short.png"
                        },
                        "start": 5,
                        "length": 95.58200000000221,
                        "fit": "crop",
                        "position": "center",
                        "opacity": 1
                    }
                ]
            },
            {
                "clips": [
                    {
                        "asset": {
                            "type": "video",
                            "src": "https:\/\/entropi.ca\/alh\/alh_bumper.mp4",
                            "volume": 1
                        },
                        "start": 0,
                        "length": 5,
                        "fit": "crop",
                        "position": "center",
                        "opacity": 1
                    },
                    {
                        "asset": {
                            "type": "image",
                            "src": "https:\/\/dl.airtable.com\/.attachments\/763f14a0cd77a642bd051461e1b9f47f\/af100781\/pexels-photo-259165.jpeg"
                        },
                        "start": 5,
                        "length": 5,
                        "fit": "crop",
                        "position": "center",
                        "transition": {
                            "out": "fade"
                        },
                        "effect": "zoomIn",
                        "opacity": 1
                    },
                    {
                        "asset": {
                            "type": "video",
                            "src": "https:\/\/dl.airtable.com\/.attachments\/7c44aed5989a77e400189210231dcdf4\/71d8ae91\/453930982.hd.mp4?ts=1653429017&userId=usrQ4kJRtjzTLK4bl&cs=eede656208f89e9e",
                            "volume": 0
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                        "start": 10,
                        "length": 4.279100000000111,
                        "fit": "crop",
                        "position": "center",
                        "opacity": 1
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                    {
                        "asset": {
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                        "opacity": 1
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                        "fit": "crop",
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                        "opacity": 1
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                        "fit": "crop",
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                        "opacity": 1
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                            "volume": 0
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                        "fit": "crop",
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                        "fit": "crop",
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                            "src": "https:\/\/entropi.ca\/alh\/like-comment-subscroob.mp4",
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                ]
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        ],
        "cache": true
    },
    "output": {
        "format": "mp4",
        "resolution": "1080",
        "fps": 29.97,
        "quality": "medium",
        "repeat": true
    },
    "callback": "https:\/\/globot.dev\/shothook\/webhook.php?shotstack=reczC8TShuh90fgK5",
    "disk": "local"
}
5

Just tried rendering the video and can reproduce the error. From my initial check it looks like the issue is related to the 29.97 fps you are using.

I was able to render the video with the correct duration using 25fps - which is the same as most of your source footage.

Is there a specific reason you’re using 29.97fps?

6

No, not a specific one—I just went with the US default out of habit since I had no reason to choose any particular rate (>=24fps). I eventually changed it to 24fps and still had the issue until I started rounding the clip lengths. That is for a specific reason: I need to generate opacity values based on the voice over audio data and, since that involves its bit values, working with a frame rate that’s divisible by two avoids truncated fractional values in subsequent calculations. I went with 24fps (as opposed to 30) because it was lower.