@DaneLLL you’re pointing to the same topic as @Jakowlew mentionned where I provided that weird sample.
@Jakowlew, this was just a one evening trial that I posted for forum users, but not sure that it can be a good template unless this works fine with your case.
The main point would be the memory flags, where I was using NVMM memory instead of system memory (that you’re using with (GstMemoryFlags)0 ).
It is usual AFAIK that buffer size in NVMM reports a lower size than actual buffer.
Probably @DaneLLL or someone else more skilled than me would be able to give more details about the reported size and actual operation