I have been using a Samsung A5 (2017, SM-A520F). Its maximum performance in video recording is 1080p, 30 FPS.

Please specify the minimum practical write speed that I need to have when I am buying a new memory card?

  • Questions about Android phones should de asked at Android Enthusiasts. Such questions are off-topic here.
    – user931000
    Oct 24 '18 at 22:39
  • 2
    It all depends on the bitrate that the device encodes to, which can be quite unrelated to the resolution or frame rate (i.e: lower resolution could have high bitrate, high resolution could have low bitrate)... See the Secure Digital Speed Class Rating for more info on how SD cards are marketed.
    – Attie
    Oct 24 '18 at 23:24
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    @GabrielaGarcia This is really about matching video bit rates to SD Card sustained write speeds. Just because Android was mentioned doesn't mean we have to throw it over the wall to another site.
    – Spiff
    Oct 25 '18 at 0:16
  • @Attie I agree with you. Thanks for sharing the Wiki article with me. Somehow, I had missed it when I was googling. Oct 25 '18 at 1:00

I ran some data rate calculations based on 1080p30, 8 bits per color, no chroma sub-sampling, high motion, and H.264 AVC compression, and came to the conclusion that 8 MegaBytes/sec should be plenty.

This accords with the Secure Digital Speed Class Rating table that @Attie linked to. Since SD has no 8 MegaBytes/sec class, the 10 MegaBytes/sec class (C10/V10) is recommended for "Full HD" 1080p30.

So I agree with those industry association recommendations. At a practical minimum, you want the V10 class that supports 10 MegaBytes/sec sustained/sequential writes.

  • Wow... such a great explanation. Cheers! Oct 25 '18 at 0:51
  • 8 MB/sec or 8 Mbit/sec? There's a huge difference.
    – user89623
    Oct 25 '18 at 1:53
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    @duskwuff Capital B for Bytes, but I'll edit it to make it explicit.
    – Spiff
    Oct 25 '18 at 2:47

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