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AVC (High@L3.2) or AVC (Main@L4)?

CC2500 -  
ziggourat Posted messages 24643 Registration date   Status Contributor Last intervention   -
Hello,

What is the difference between these two MP4 files, both derived from an MP4 file converted separately and individually by HandBrake?

Regarding the encoding:

One is heavier, with the following information:

AVC (High@L3.2) (CABAC / 2 Ref Frames)

And the other is lighter with the following information:
AVC (Main@L4) (CABAC / 4 Ref Frames)

Can I trust the second file and upload it to a personal website and also to YouTube?

Thank you in advance.

1 answer

  1.
    glandu Posted messages 25506 Registration date   Status Contributor Last intervention   4 090
     
    Hello, this gives me the opportunity to revisit the codecs
    to make it very short, your "format" of compression is indeed h264AVC cabac which is an arithmetic coding entropy technique meaning it is supposed to reduce the artifacts present in block transformation coding, check the web for more details
    As for 2Ref Frames and 4 ref Frames, it is the choice to create intermediate images between the full images (interlacing)

    "Donkeys change their minds, not fools"
    remember to mark your message as "resolved" if that is the case
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    1. ziggourat Posted messages 24643 Registration date   Status Contributor Last intervention   5 340
       
      Hello,

      Baseline, Main, High (4, 4:1, 4:2:2) are profiles of the H264 or MPEG-4 AVC standard (the H264/AVC codec if you will...) : https://fr.wikipedia.org/wiki/H.264#Profils
      The higher the profile, the more complex the calculations the software must perform, and thus, theoretically, it can take more time. After that, it depends on the power of your computer.
      You might want to read this topic: https://www.repaire.net/forums/discussions/profil-du-format-baseline.281364/
      To summarize, taken from GypseVidéo, a site dedicated to editing:
      - Baseline Profile (BP): not suitable for complex edits (camera movements, effects...). Used by low-end hardware: mobiles, tablets...
      - Main Profile (MP): for consumer applications, supplanted by the more precise High profile.
      - High Profile (HiP): a good compromise between Main and higher profiles. High 10 (Hi10P): offers superior precision compared to High. High 4.2.2 (Hi422P): for professional applications.

      To add to what glandu said, the same applies to Reference Images, as explained by gej62 here: https://forums.commentcamarche.net/forum/affich-25434300-modifier-les-ref-frames-d-une-video
      You notice that gej62 adapted the value of the parameters to be set in the software according to that of the original file. This is generally what we do in video encoding in order to be "as faithful" to the video being processed, if I may say so. Except, of course, if the purpose of exporting is specific (reducing file size, uploading, etc.), in which case, we adapt the values to match the intended goal. Sometimes, compromises must be made.
      Two definitions if you're interested on Wikipedia:
      - GOP: https://fr.wikipedia.org/wiki/Group_of_pictures
      - Reference Image: https://fr.wikipedia.org/wiki/Image_de_r%C3%A9f%C3%A9rence

      Finally, normally, even if you set a different profile with and/or different Reference Images, the file size should not vary in principle. What can make it heavier or lighter is the bitrate or video bitrate value, essentially expressed in Kbps for example.
      In your case, you indicate that after encoding with 2 distinct profiles, one is heavier than the other. Are you sure the bitrate/video bitrate is the same?

      As for uploading it online, you can use the preconfigured profiles in the software (for HandBrake, it's Vimeo I believe) that you modify based on the data of your original file (FPS, resolution mainly; for the bitrate, it's up to you), or rely on the encoding parameters outlined by YouTube: https://support.google.com/youtube/answer/1722171?hl=fr
      The larger the file, the longer it will take to upload... and for your site, it will occupy more space...

      See JDN for some encoding tips: https://www.journaldunet.com/media/publishers/1108945-5-conseils-sur-l-encodage-ce-passage-oblige-pour-mener-a-bien-votre-strategie-video/

      All this, to respond to you, yes, you can trust the 2nd file if the result satisfies you, especially after being uploaded online.

      Kind regards
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      1. CC2500 > ziggourat Posted messages 24643 Registration date   Status Contributor Last intervention  
         
        Hello,

        I would like to thank "glandu" and "ziggourat" very much for their answers to my questions.
        In particular, "ziggourat"'s response is very detailed and well-referenced, and it has given me the courage to continue my efforts.

        Regarding the "bitrate/debit" of the two files, according to the information displayed by "Media Info", both files are identical.

        The larger file:
        AVC (High@L3.2) (CABAC / 2 Ref Frames)

        was produced according to a "HandBrake" preset for YouTube.

        And the smaller file:

        AVC (Main@L4) (CABAC / 4 Ref Frames)

        according to custom settings.

        Thank you again a thousand times.
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      2. ziggourat Posted messages 24643 Registration date   Status Contributor Last intervention   5 340 > CC2500
         
        Thank you, this has allowed me to dive back into the intricacies of the H264 codec, putting aside my "bad" little habits ;-)
        "
        Regarding the "bitrate" of the two files, according to the information displayed by "Media Info", both files are identical
        ." : for me and based on my tests carried out with Avidemux, this is not possible, see Image :
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    2. CC2500
       
      Hello,

      Thank you very much for your response.
      Below, in my thanks to "ziggourat" for their detailed and referenced answer, I thanked you once again.

      Best regards
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