Bug 425806

SUMMARY
When working on a large project with a lot of files, Kdenlive will get killed by the Linux kernel for "out of memory", consuming a total of 6 GB of RAM out of 8.
It seems to be trying to open all the files and put them in RAM, causing it to consume lots of memory when working on multiple big files (for example I was working with 200+ 4K images and hours of 720p video).

STEPS TO REPRODUCE
1. Install Kdenlive
2. Open or create a big project with a lot of files
3. Wait for Linux to kill it

OBSERVED RESULT
The whole system freeze and Kdenlive get killed because of using 6 GB of RAM.

EXPECTED RESULT
Kdenlive will consume 1 or 2 GB of RAM and edit smoothly.

SOFTWARE/OS VERSIONS
Linux: 5.4.60-2
KDE Plasma Version: 5.19.80
Kdenlive Version: 20.08.0
KDE Frameworks Version: 5.74.0
Qt Version: 5.15.0

ADDITIONAL INFORMATION
Output of 'dmesg':
[11183.714476] oom-kill:constraint=CONSTRAINT_NONE,nodemask=(null),cpuset=/,mems_allowed=0,global_oom,task_memcg=/user.slice/user-1000.slice/user@1000.service,task=kdenlive,pid=65963,uid=1000
[11183.714660] Out of memory: Killed process 65963 (kdenlive) total-vm:6817836kB, anon-rss:3856256kB, file-rss:0kB, shmem-rss:5924kB, UID:1000 pgtables:9520kB oom_score_adj:0
[11184.049000] oom_reaper: reaped process 65963 (kdenlive), now anon-rss:0kB, file-rss:0kB, shmem-rss:5936kB