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• checkasm : Serialize read_time() calls on x86

  8 octobre 2014, par Henrik Gramner

  checkasm : Serialize read_time() calls on x86
  Improves the accuracy of benchmarks, especially in short functions.
  To quote the Intel 64 and IA-32 Architectures Software Developer’s Manual :
  
  "The RDTSC instruction is not a serializing instruction. It does not necessarily
  
  wait until all previous instructions have been executed before reading the counter.
  
  Similarly, subsequent instructions may begin execution before the read operation
  
  is performed. If software requires RDTSC to be executed only after all previous
  
  instructions have completed locally, it can either use RDTSCP (if the processor
  
  supports that instruction) or execute the sequence LFENCE ;RDTSC."
  RDTSCP would accomplish the same task, but it’s only available since Nehalem.
  This change makes SSE2 a requirement to run checkasm.
  

  • [DH] tools/checkasm.c

• ffmpeg randomly stops recording rtmp stream

  14 novembre 2022, par M9A

  I am trying to record a rtmp stream using ffmpeg. On the whole it records the stream fine but every so often it stops recording the stream and when I then go to record it again, it will only record around a second or 2 before it stops again. This usually goes on for like 10-15mins. In this time if I want to record the stream, I would have to manually record 1-2 seconds each time. This sounds like it is a server issue - perhaps there is a mechanism that cuts off the stream every few seconds.

  


  In the case where the stream cuts off, is there a way to keep trying and recording all of these 1-2 second segments rather than me doing it manually ? Doing it manually creates gaps in the recording due to the time taken to connect and record the stream. I even tried running the command in a loop but even with that there are gaps in the video.

  


  The code I am using to record the stream is as follows :

  


  ffmpeg -i "rtmp://example.com/stream?id=12345" -vcodec copy -acoded copy "output.mp4"


  


  When it is recording fine and cuts off the first time, there is no error given. It's like the stream came to an end so it stops recording. The subsequent times where I can only record 1-2 seconds are the same - there is no error

  


  As there are no error messages such as timeout or connection errors, I cannot even run flags on the command to retry recording.

  


• How to detetc hardware acceleration in ffmpeg

  19 décembre 2020, par Ali Razmkhah

  I am writing c++ program to screen record by ffmpeg 4.3 ! I need to detect hardware acceleration support such as h264_qsv or h264_nvenc without running ffmpeg.exe !

  


  I explored ffmpeg.exe source code and found no results ! some solutions are deprecated or dose not work on 4.3 !
As instance,

  


  avcodec_find_encoder_by_name("h264_qsv")


  


  returns null even it is exist and works properly !