Demo
Tux's lil' helper
Joined: 25 Nov 2022
Posts: 126
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 Posted: Fri Jun 21, 2024 7:11 pm Post subject: General questions about ffmpeg transcoding |
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Hello folks ...
I'm a ffmpeg noob, I don't know much about it except for a basic idea about encoding/decoding and a few videos I watched over youtube about it's usage. I also don't have a big background in digital video, I only watch he occasional movie or course or stream, etc....
I have an intel machine with an i7-6700 which is slow. And I have a 30 Gig folder of lectures encoded in old real media format ".rm" and I was trying ffmpeg on it.
| Code: | | ffmpeg -init_hw_device "vulkan=vk:0" -hwaccel vulkan -hwaccel_output_format vulkan -i input.rm -c:v hevc output.mp4 |
The result was impressive, the input file was 144 meg, the output was 95 meg which is a little over 30% reduction.
40%+ came out with avi files also which made me interested in knowing more about ffmpeg, and leads me to the question behind the post, why did I get such big size reduction in video output? Is it just more efficient compression ratio for x265 format or there was comparable data loss from the original files? And how would I measure that data loss? What tools to use if any to see what kind of data was in the input and what came out in the output?
Trying the crf switch with 18 always generates larger files than the input which's the reason why I'm asking.
One thing more I wanted to mention, vulkan as an acceleration option seems to be sketchy, working sometimes and not all the time, qsv on the other hand is not working at all, what should I do to get them to work?
I do have the media-libs/oneVPL-intel-gpu-24.2.2 installed, media-libs/mesa-24.1.1 as well. I need to mention also that I tweaked mesa to only compile iris and vulkan, neither crocus_dri.so, swrast_dri.so, libvulkan_intel_hasvk.so are built. I don't see any difference in functionality with them not being built.
Thank you! |
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