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• MLT melt slideshow on Windows : unable to control output video length and problems with using wildcards

  10 novembre 2020, par Tjk

  I am using the following command within a batch script to, hopefully, eventually programmatically create simple video slideshows with transitions :

  


  melt 131.jpg 132.jpg 133.jpg ttl=75 -attach crop center=1 -filter luma cycle=75 duration=25 -transition mix -consumer avformat:out.mp4 frame_rate_num=30 frame_rate_den=1


  


  Most of this command is an adaptation for Windows of this command on the MLT website blog (with the exception of the part that scales and transforms the image). For some reason when I run this, however, the output video file is 25 minutes long !

  


  I have two main questions :

  


  a. How do I properly control the duration of each image in the video ? I have experimented quite a bit with changing the parameters and I have a semi-decent understanding of what they all mean (I am a newbie to MLT but I figured that there's no way to do something like this easily in FFMPEG alone). The only way I have found to decrease the duration with any amount of control is to increase the output framerate to absurd numbers (which, of course, is not ideal as it's a massive waste of time and energy and still doesn't really solve the issue).

  


  b. How do I use a wildcard to input all the .jpg files in a folder on Windows ? I tried adding *.jpg but that didn't work and I don't know how else to do it within a batch script (I tried using the following code to get the file names as a variable, but I wasn't able to get string concatenation working correctly because it only outputs the final file name)

  


  set files=
for /r %%i in (*.jpg) do (
    echo %%i
    set files=%files% "%%i"
)
echo %files%


  


  Thank you for any suggestions !

  


• Revision d36852b702 : Add encoding option —static-thresh This option exists in VP8, and it was rewri

  11 juillet 2013, par Yunqing Wang

  Changed Paths :
   Modify /vp9/encoder/vp9_encodeframe.c

  
   Modify /vp9/encoder/vp9_rdopt.c

  
  
  Add encoding option —static-thresh

  This option exists in VP8, and it was rewritten in VP9 to support
  skipping on different partition levels. After prediction is done,
  we can check if the residuals in the partition block will be all
  quantized to 0. If this is true, the skip flag is set, and only
  prediction data are needed in reconstruction. Based on DCT's energy
  conservation property, the skipping check can be estimated in
  spatial domain.

  The prediction error is calculated and compared to a threshold.
  The threshold is determined by the dequant values, and also
  adjusted by partition sizes. To be precise, the DC and AC parts
  for Y, U, and V planes are checked to decide skipping or not.

  Test showed that
  1. derf set :
  when static-thresh = 1, psnr loss is 0.666% ;
  when static-thresh = 500, psnr loss is 1.162% ;
  2. stdhd set :
  when static-thresh = 1, psnr loss is 1.249% ;
  when static-thresh = 500, psnr loss is 1.668% ;

  For different clips, encoding speedup range is between several
  percentage and 20+% when static-thresh <= 500. For example,
  clip bitrate static-thresh psnr time
  akiyo(cif) 500 0 48.923 5.635s(50f)
  akiyo 500 500 48.863 4.402s(50f)

  parkjoy(1080p) 4000 0 30.380 77.54s(30f)
  parkjoy 4000 500 30.384 69.59s(30f)

  sunflower(1080p) 4000 0 44.461 85.2s(30f)
  sunflower 4000 500 44.418 78.1s(30f)

  Higher static-thresh values give larger speedup with larger
  quality loss.

  Change-Id : I857031ceb466ff314ab580ac5ec5d18542203c53

• AAC encoder : Extensive improvements

  11 octobre 2015, par Claudio Freire

  AAC encoder : Extensive improvements
  This finalizes merging of the work in the patches in ticket #2686.
  Improvements to twoloop and RC logic are extensive.
  The non-exhaustive list of twoloop improvments includes :
  
   - Tweaks to distortion limits on the RD optimization phase of twoloop
  
   - Deeper search in twoloop
  
   - PNS information marking to let twoloop decide when to use it
  
     (turned out having the decision made separately wasn’t working)
  
   - Tonal band detection and priorization
  
   - Better band energy conservation rules
  
   - Strict hole avoidance
  For rate control :
  
   - Use psymodel’s bit allocation to allow proper use of the bit
  
     reservoir. Don’t work against the bit reservoir by moving lambda
  
     in the opposite direction when psymodel decides to allocate more/less
  
     bits to a frame.
  
   - Retry the encode if the effective rate lies outside a reasonable
  
     margin of psymodel’s allocation or the selected ABR.
  
   - Log average lambda at the end. Useful info for everyone, but especially
  
     for tuning of the various encoder constants that relate to lambda
  
     feedback.
  Psy :
  
   - Do not apply lowpass with a FIR filter, instead just let the coder
  
     zero bands above the cutoff. The FIR filter induces group delay,
  
     and while zeroing bands causes ripple, it’s lost in the quantization
  
     noise.
  
   - Experimental VBR bit allocation code
  
   - Tweak automatic lowpass filter threshold to maximize audio bandwidth
  
     at all bitrates while still providing acceptable, stable quality.
  I/S :
  
   - Phase decision fixes. Unrelated to #2686, but the bugs only surfaced
  
     when the merge was finalized. Measure I/S band energy accounting for
  
     phase, and prevent I/S and M/S from being applied both.
  PNS :
  
   - Avoid marking short bands with PNS when they’re part of a window
  
     group in which there’s a large variation of energy from one window
  
     to the next. PNS can’t preserve those and the effect is extremely
  
     noticeable.
  M/S :
  
   - Implement BMLD protection similar to the specified in
  
     ISO-IEC/13818:7-2003, Appendix C Section 6.1. Since M/S decision
  
     doesn’t conform to section 6.1, a different method had to be
  
     implemented, but should provide equivalent protection.
  
   - Move the decision logic closer to the method specified in
  
     ISO-IEC/13818:7-2003, Appendix C Section 6.1. Specifically,
  
     make sure M/S needs less bits than dual stereo.
  
   - Don’t apply M/S in bands that are using I/S
  Now, this of course needed adjustments in the compare targets and
  
  fuzz factors of the AAC encoder’s fate tests, but if wondering why
  
  the targets go up (more distortion), consider the previous coder
  
  was using too many bits on LF content (far more than required by
  
  psy), and thus those signals will now be more distorted, not less.
  The extra distortion isn’t audible though, I carried extensive
  
  ABX testing to make sure.
  A very similar patch was also extensively tested by Kamendo2 in
  
  the context of #2686.
  

  • [DH] Changelog
  • [DH] libavcodec/aac.h
  • [DH] libavcodec/aaccoder.c
  • [DH] libavcodec/aaccoder_trellis.h
  • [DH] libavcodec/aaccoder_twoloop.h
  • [DH] libavcodec/aacenc.c
  • [DH] libavcodec/aacenc.h
  • [DH] libavcodec/aacenc_is.c
  • [DH] libavcodec/aacenc_is.h
  • [DH] libavcodec/aacenc_pred.c
  • [DH] libavcodec/aacenc_quantization.h
  • [DH] libavcodec/aacenc_utils.h
  • [DH] libavcodec/aacpsy.c
  • [DH] libavcodec/mathops.h
  • [DH] libavcodec/mips/aaccoder_mips.c
  • [DH] libavcodec/psymodel.c
  • [DH] libavcodec/psymodel.h
  • [DH] tests/fate/aac.mak