Thumbnail error

General
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1

Good morning everyone again!!

I’m having the following problem with thumbnails.
I’m using CasparCG 2.4.3 on Ubuntu 22.04 Desktop.

I add several files throughout the day to play in Caspar — I do this by copying them into the folder defined in my caspar.config.
For several days everything worked fine, but one day my playout could no longer get the thumbnails for any files. When I send the command
THUMBNAIL RETRIEVE <MediaPath> or CINF <MediaPath>, Caspar returns an error as if the file doesn’t exist.

Here’s the error:

THUMBNAIL RETRIEVE SENS/NOV/03/HD/fernanda_davi
[2025-10-15 13:38:16.721] [error]   Exception: ./src/protocol/util/http_request.cpp(72): Throw in function caspar::http::HTTPResponse caspar::http::request(const string&, const string&, const string&)
[2025-10-15 13:38:16.721] [error]   Dynamic exception type: boost::wrapexcept<caspar::io_error>
[2025-10-15 13:38:16.721] [error]   [caspar::tag_msg_info*] = Invalid Response
[2025-10-15 13:38:16.721] [error]   [caspar::tag_stacktrace_info*] =  0# 0x000060CC81E036FD in casparcg-server-2.4

The only way to fix this error is by running the command THUMBNAIL GENERATE_ALL, or by restarting both Caspar and the Scanner.

My question is: do I need to periodically restart Caspar and the Scanner, or should I run the THUMBNAIL GENERATE_ALL command instead?

Has anyone else experienced this problem?
Is there a better solution for this error?

Thanks everyone for the help!

2

Does anyone have a suggestion on what I should do to keep the thumbnails always up to date and available???

Thank you very much.

3

I do not have a direct answer for your question, but my (mostly Windows) experience of the scanner system is that it is very stable in operation.

Bit it is both interesting and slightly odd that issuing an AMCP THUMBNAIL GENERATE_ALL request reactivates the link between the server and the scanner.

The CasparCG server code, in module AMCPCommandsImpl.c++ lines 1436 to 1439, converts the AMCP command into an http request to the scanner to run “/thumbnail/generate”. In the scanner code (version 1.3.4) the request arrives at line 196 of module src/app.ts. The current behaviour is to do nothing with the request, returning a 202 THUMBNAIL GENERATE_ALL OK status.

Have you tried using an http requests to the scanner to see if it responds when your server is seeing errors? For example using a browser to access:

http://<scanner_dotted_ip>:8000/media/thumbnail/<thumbnail_name>

For a browser on same computer as the scanner:

http://127.0.0.1:8000/media/thumbnail/<thumbnail_name>

This request returns and displays the .PNG thumbnail in the browser. If you can test this access when your server fails to get the thumbnail via AMCP, it may help determine if the error is in the server processing of the thumbnail fetch request.

You can also use http to fetch the base64 version of the thumbnail via an http access to:

http://<scanner_dotted_ip>:8000/thumbnail/<thumbnail_name>
4

Thank you very much for your reply. I’ll check out your suggestions when the error happens to me.