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• swresample/resample : improve bessel function accuracy and speed

  2 novembre 2015, par Ganesh Ajjanagadde

  swresample/resample : improve bessel function accuracy and speed
  This improves accuracy for the bessel function at large arguments, and this in turn
  
  should improve the quality of the Kaiser window. It also improves the
  
  performance of the bessel function and hence build_filter by 20%.
  
  Details are given below.
  Algorithm : taken from the Boost project, who have done a detailed
  
  investigation of the accuracy of their method, as compared with e.g the
  
  GNU Scientific Library (GSL) :
  
  http://www.boost.org/doc/libs/1_52_0/libs/math/doc/sf_and_dist/html/math_toolkit/special/bessel/mbessel.html.
  
  Boost source code (also cited and licensed in the code) :
  
  https://searchcode.com/codesearch/view/14918379/.
  Accuracy : sample values may be obtained as follows. i0 denotes the old bessel code,
  
  i0_boost the approach here, and i0_real an arbitrary precision result (truncated) from Wolfram Alpha :
  
  type "bessel i0(6.0)" to reproduce. These are evaluation points that occur for
  
  the default kaiser_beta = 9.
  Some illustrations :
  
  bessel(8.0)
  
  i0      (8.000000) = 427.564115721804739678191254
  
  i0_boost(8.000000) = 427.564115721804796521610115
  
  i0_real (8.000000) = 427.564115721804785177396791
  bessel(6.0)
  
  i0      (6.000000) = 67.234406976477956163762428
  
  i0_boost(6.000000) = 67.234406976477970374617144
  
  i0_real (6.000000) = 67.234406976477975326188025
  Reason for accuracy : Main accuracy benefits come at larger bessel arguments, where the
  
  Taylor-Maclaurin method is not that good : 23+ iterations
  
  (at large arguments, since the series is about 0) can cause
  
  significant floating point error accumulation.
  Benchmarks : Obtained on x86-64, Haswell, GNU/Linux via a loop calling
  
  build_filter 1000 times :
  
  test : fate-swr-resample-dblp-44100-2626
  new :
  
  995894468 decicycles in build_filter(loop 1000),     256 runs,      0 skips
  
  1029719302 decicycles in build_filter(loop 1000),     512 runs,      0 skips
  
  984101131 decicycles in build_filter(loop 1000),    1024 runs,      0 skips
  old :
  
  1250020763 decicycles in build_filter(loop 1000),     256 runs,      0 skips
  
  1246353282 decicycles in build_filter(loop 1000),     512 runs,      0 skips
  
  1220017565 decicycles in build_filter(loop 1000),    1024 runs,      0 skips
  A further 5% may be squeezed by enabling -ftree-vectorize. However,
  
  this is a separate issue from this patch.
  Reviewed-by : Michael Niedermayer <michael@niedermayer.cc>
  
  Signed-off-by : Ganesh Ajjanagadde <gajjanagadde@gmail.com>
  

  • [DH] libswresample/resample.c

• Streams stop when creating a quad split Multi-viewer using FFMPEG [closed]

  6 avril 2024, par Chris Parker

  Created a FFMPEG script that takes in 4 SRT Live Streams and displays them in a quad split MV. However when I launch this script all 4 SRT streams will play but 3 will pause and 1 will play.

  


  ffmpeg \
-re -hwaccel auto -hwaccel_output_csp videocore \
-stream_loop -1 \
-i "srt://address:5000?streamid=stream-id" \
-stream_loop -1 \
-i "srt://address:5000?streamid=stream-id" \
-stream_loop -1 \
-i "srt://address:5000?streamid=stream-id" \
-stream_loop -1 \
-i "srt://address:5000?streamid=stream-id" \
-filter_complex "\
[0]scale=1920x1080,setdar=16/9[a];\
[1]scale=1920x1080,setdar=16/9[b];\
[2]scale=1920x1080,setdar=16/9[c];\
[3]scale=1920x1080,setdar=16/9[d];\
[a][b][c][d]xstack=inputs=4:layout=0_0|w0_0|0_h0|w0_h0[v]" \
-map "[v]" \
-c:v libx264 -preset veryfast -crf 28 \
-pix_fmt yuv420p -g 48 -bf 2 -refs 4 \
-f mpegts -b:v 10M -maxrate:v 15M -bufsize:v 30M \
-fflags +discardcorrupt -reset_timestamps 1 \
"srt://address:5000?streamid=stream-id"


  


  getting a lot of the below error ;

  


  16:48:49.628704/SRT:RcvQ:w2!W:SRT.qr: @214003038:No room to store incoming packet seqno 649744568, insert offset 7190. Space avail 0/8192 pkts. (TSBPD ready in -12342ms, timespan 6093 ms). GETTIME_MONOTONIC drift 0 ms.


  


  I've tried smaller resolution and adjusting buffer sizes as well as the other flags but I'm not sure what else I can do.

  


• How to edit video (cut some scenes) without increasing the video's size

  18 février 2016, par 123iamking

  [Introduction]

  I have a video : Input.mp4 - length : 29 min 6 sec - size : 120 MB

  I use Microsoft Movie Maker 2012 (Movie Maker is included in the Windows Essentials 2012 program suite), to cut some boring scenes and keep the cool scenes and I get the video : Output.mp4 - length : 15 min 22 sec - size : 155 MB.

  And it’s take a long time to create the Output.mp4 and the size is ridiculously increased. I can’t use this kind of software anymore, I need to create a new software to serve my purpose.

  [Question]

  Is there anyway with C# .Net to simply cut and merge video without increasing the video’s size and have to be fast ?

  [What I have tried]

  I intend to use ffmpeg to cut the clip and merge the clip and I found something about cut video here , but the console said something about "Timestamps are unset in a packet for stream 0. This is deprecated and will stop working in the future." - should I still use this ?

  Should I use ffmpeg or there’s better way to do this.