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• Does Apple AS assembler replace certain NEON instructions with equivalent ones on iOS ?

  5 avril 2012, par Yi Wang

  I was trying to use ffmpeg on iOS and was debugging a crash in the optimized arm code. I have discovered that some unsigned (.u16, .u32) instruction have been replaced by signed ones (.i16, .i32). It's easy to see because disassembled instruction on GDB doesn't quite match the source code.

  For example,

  vrshrn.u32 -> vrshrn.i32
  
  vrshrn.u16 -> vrshrn.i16
  
  vadd.u16 -> vadd.i16

  My questions :

  1. Is this behavior correct and expected ? If not, how do we correct it ?
  2. If they are equivalent, why do we nee need the unsigned ones at all ? Is it because that way the code is more explicit ?
  3. Is this behavior expected with other platform's toolkit ? For example, Android's toolkit ? (I have heard Apple's AS is an ancient one)

• h265_videotoolbox for Apple Chips Not working with ffmpeg

  22 janvier 2024, par Martin Julien

  I have a 16-inch Macbook Pro.
System :
Model Name : MacBook Pro
Chip : Apple M1 Max
Total Number of Cores : 10 (8 performance and 2 efficiency)
Memory : 64 GB

  


  You can take advantage of apple chips to encode faster by replacing the usual line :
-c:v libx265 by -c:v h265_videotoolbox.

  


  Here's an example.
Since h265 doesn't work at the moment, here's a line that works just fine :

  


  for i in *.mp4; do ffmpeg -i "$i" -c:v h264_videotoolbox -b:v 2000k -c:a aac -b:a 192k -s 1920x1080 -threads 8 "${i%.*}_1.mp4"; done

  


  The version of ffmpeg installed on my mac is the latest : 6.1.1

  


  My problem :
I want to encode in h265. My command line is :
for i in *.mp4; do ffmpeg -i "$i" -c:v h265_videotoolbox -b:v 2000k -c:a aac -b:a 192k -s 1920x1080 -threads 8 "${i%.*}_1.mp4"; done

  


  Everything should work in theory. But I get this from the Shell :

  


  [vost#0:0 @ 0x150f06fd0] Unknown encoder 'h265_videotoolbox' [vost#0:0 @ 0x150f06fd0] Error selecting an encoder Error opening output file Denis_1.mp4. Error opening output files: Encoder not found

  


  My attempts :

  


  I spent a lot of time with ChatGPT to solve the problem, but nothing worked. So I'm asking the question here to see if anyone has had the same problem as me and if there's a solution to fix it.

  


  Thank you for your help,

  


  best regards,
Martin

  


• ppc : Drop support for Apple GCC

  12 juin 2017, par Diego Biurrun

  ppc : Drop support for Apple GCC
  Apple GCC has not been a thing anymore on PowerPC since many years.
  

  • [DBH] configure
  • [DBH] libavutil/ppc/util_altivec.h