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After converting from .mov into .mp4, a video file is greatly reduced in size (.mov - 75,2mb .mp4 - 11,9mb) - does this mean that the converted video degraded (loss of color information, or the information in the highlights/shadows, or something else) or such difference in file size can be lossless?

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    If it's for playback use, and not further editing/processing, all that matters is if the output quality looks good. Quite likely, the conversion wasn't mathematically lossless. Anyway, which tool did you use, and with what settings?
    – Gyan
    Jun 2, 2016 at 7:16
  • @Mulvya I used Miro video converter. I need to convert these videos without loss of quality for video editing. But since I have a lot of videos, I'm looking for a converter that can convert many videos with the same conversion settings (rather than manually convert each video one after the other). Could you advise me a converter which is able to convert a large amount of videos without loss of quality, for Mac?
    – Rumata
    Jun 2, 2016 at 9:40
  • @Mulvya settings: prntscr.com/bbdzgn
    – Rumata
    Jun 2, 2016 at 11:09
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    Use Handbrake.
    – Gyan
    Jun 2, 2016 at 13:52
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    Not that I know of, but I don't use it much. Make a folder, shift all the files you want in there and select that. As for size, increase the Constant Quality value in the video tab for smaller files.
    – Gyan
    Jun 4, 2016 at 18:17

1 Answer 1

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Let me explain you from scratch.

MOV, MP4, AVI, MKV etc all these are just containers, It is just kind of wrapper which contains audio, video, text, metadata file together as one file. It does not play a big role in the size of a file.

Size of the file heavily depends on audio and video codec and bit-rate of that audio video codecs.

So there is a possibility for file size reduction during conversion.

  1. Reduce in video codec bitrate. While converting video if default/changed bitrate of video codec is less than source file, then it will lead to a reduction in file size as well as quality for sure.[ May not be perceivable by eye ]

  2. Change video codec. While converting video if change video codec to advance video codec of the stream, then it will reduce size but quality will not be degraded.

For example : Video codec of a source file is MPEG-2 with bit-rate 20mbps and during conversation we convert to H264/AVC with bitrate 10mbps it will have the same quality with half of the size.

So, Below are the popular video codecs generation and improvement.

MPEG-2 -> H264 (40-50% bitrate reduction than MPEG-2) -> H265/HEVC (40-50% bitrate reduction than H264)

Though the more advanced codecs are computationally expensive during video playback. e.g H265 is ~300% more computationally expensive than H264.

During video conversation point 1. & 2. both can be applied

You can view details of audio/video file can be seen using a free tool (mediainfo) It will show properties of the stream like video codec, bitrate, fps etc.

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  • Thank you very much for this detailed answer! This is very helpful to me!
    – Rumata
    Jun 4, 2016 at 17:31
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    Worth noting that the computationally intensive nature of h.265 and h.264 make them less suitable for editing. A codec that uses more space for the same perceived quality but which requires less processing per frame might be better. Have a look at Avid DNxHR or GoPro Cineform, which are good, free editing codecs.
    – stib
    Nov 27, 2018 at 3:00

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