3 ms·

But what part gets multi threading? Because the video compression is already multithreaded. Video decompression I am not sure. And I think anything else is fair

by cm2187 3y ago

But what part gets multi threading? Because the video compression is already multithreaded. Video decompression I am not sure. And I think anything else is fairly small in comparison in term of performance cost. All improvements are welcome but I would expect the impact to be fairly immaterial in practice.

jamal-kumar 3y ago
From what I understand the more you increase multithreading with ffmpeg the more you get quality issues... If they have started to solve that problem then I will be a much happier camper
- jbk 3y ago
  > From what I understand the more you increase multithreading with ffmpeg the more you get quality issues... No. If you don't max out your CPU, you will not have quality issues.
raphaelj 3y ago
Well, that's the very specific command I'm using in one of my webapps (https://datethis.app https://datethis.app), and it's one of the main performance hotspots, so it's very *not* immaterial.
- timvdalen 3y ago
  Wow, I learned something today, did not know this was a thing!
- j1elo 3y ago
  Very interesting! I had seen the "learn more" video already, but it stayed in a corner of my mind. To compare any given piece of sound with reference sounds for ENF analysis, the references must have been recorded to start with. The fact that a webapp like yours can exist... does it mean that we, indeed, have recordings of electrical hum spanning years and years? Are they freely available, or are they commercial products? It seems so crazy to me that someone decided to put a recorder next to a humming line just to be able to later in the future match the sound with some other recordings...
  - raphaelj 3y ago
    For Europe, there are academic and public organizations that publish these ENF backlog since about 2017. For US, I couldn't find any open dataset. For these regions, I'm basically recording the sound of an A/C motor to get the reference data, but I only have a few months of backlog. See here for the coverage of the webapp: https://datethis.app/coverage https://datethis.app/coverage
    - garblegarble 3y ago
      I notice in your coverage plot, the UK National Grid data appears to end mid-2023... have they stopped providing this data?
      - raphaelj 3y ago
        No, but they do not provide the data in real time.
        deleted 3y ago
        [deleted]
drewtato 3y ago
This is removing the video stream (-vn) so that's not involved. Not sure which parts are in parallel here, but I'm guessing decoding and encoding the audio.
izacus 3y ago
Threading depends on implementation of each encoder/decoder - most video encoders and decoders are multithreaded, audio ones not so much. At least that was the state of the world the last time I've looked into ffmpeg internals.
pjc50 3y ago
Multithreading the filter graph itself at the top level, so "decode", "sample rate convert", and "encode" can be in separate threads.
account42 3y ago
Video compression (at least x264/x265) has a maximum number of threads it can use depending on the video resolution. This means that e.g. for 1080p ffmpeg cannot fully utilize a 64-thread CPU.

by cm2187 3y ago

jamal-kumar 3y ago

From what I understand the more you increase multithreading with ffmpeg the more you get quality issues... If they have started to solve that problem then I will be a much happier camper

jbk 3y ago
> From what I understand the more you increase multithreading with ffmpeg the more you get quality issues... No. If you don't max out your CPU, you will not have quality issues.

raphaelj 3y ago

Well, that's the very specific command I'm using in one of my webapps (https://datethis.app https://datethis.app), and it's one of the main performance hotspots, so it's very *not* immaterial.

timvdalen 3y ago
Wow, I learned something today, did not know this was a thing!
j1elo 3y ago
Very interesting! I had seen the "learn more" video already, but it stayed in a corner of my mind. To compare any given piece of sound with reference sounds for ENF analysis, the references must have been recorded to start with. The fact that a webapp like yours can exist... does it mean that we, indeed, have recordings of electrical hum spanning years and years? Are they freely available, or are they commercial products? It seems so crazy to me that someone decided to put a recorder next to a humming line just to be able to later in the future match the sound with some other recordings...
- raphaelj 3y ago
  For Europe, there are academic and public organizations that publish these ENF backlog since about 2017. For US, I couldn't find any open dataset. For these regions, I'm basically recording the sound of an A/C motor to get the reference data, but I only have a few months of backlog. See here for the coverage of the webapp: https://datethis.app/coverage https://datethis.app/coverage
  - garblegarble 3y ago
    I notice in your coverage plot, the UK National Grid data appears to end mid-2023... have they stopped providing this data?
    - raphaelj 3y ago
      No, but they do not provide the data in real time.
      - deleted 3y ago
        [deleted]

drewtato 3y ago

This is removing the video stream (-vn) so that's not involved. Not sure which parts are in parallel here, but I'm guessing decoding and encoding the audio.

izacus 3y ago

Threading depends on implementation of each encoder/decoder - most video encoders and decoders are multithreaded, audio ones not so much. At least that was the state of the world the last time I've looked into ffmpeg internals.

pjc50 3y ago

Multithreading the filter graph itself at the top level, so "decode", "sample rate convert", and "encode" can be in separate threads.

account42 3y ago

Video compression (at least x264/x265) has a maximum number of threads it can use depending on the video resolution. This means that e.g. for 1080p ffmpeg cannot fully utilize a 64-thread CPU.