Recherche avancée

Sur d’autres sites (5478)

• Convert image sequence to video using ffmpeg and list of files

  13 mai 2015, par rensa

  I have a camera taking time-lapse shots every 2–3 seconds, and I keep a rolling record of a few days’ worth. Because that’s a lot of files, I keep them in subdirectories by day and hour :

  images/
  
      2015-05-02/
  
          00/
  
              2015-05-02-0000-02
  
              2015-05-02-0000-05
  
              2015-05-02-0000-07
  
          01/
  
              (etc.)
  
      2015-05-03/

  I’m writing a script to automatically upload a timelapse of the sunrise to YouTube each day. I can get the sunrise time from the web in advance, then go back after the sunrise and get a list of the files that were taken in that period using find :

  touch -d "$SUNRISE_START" sunrise-start.txt
  
  touch -d "$SUNRISE_END" sunrise-end.txt
  
  find images/"$TODAY" -type f -anewer sunrise-start.txt ! -anewer sunrise-end.txt

  Now I want to convert those files to a video with ffmpeg. Ideally I’d like to do this without making a copy of all the files (because we’re talking 3.5 GB per hour of images), and I’d prefer not to rename them to something like image000n.jpg because other users may want to access the images. Copying the images is my fallback.

  But I’m getting stuck sending the results of find to ffmpeg. I understand that ffmpeg can expand wildcards internally, but I’m not sure that this is going to work where the files aren’t all in one directory. I also see a few people using find’s --exec option with ffmpeg to do batch conversions, but I’m not sure if this is going to work with image sequence input (as opposed to, say, converting 1000 images into 1000 single-frame videos).

  Any ideas on how I can connect the two—or, failing that, a better way to get files in a date range across several subdirectories into ffmpeg as an image sequence ?

• Official RealVideo Specifications

  29 juillet 2010, par Multimedia Mike — General

  A little birdie tipped me off to a publicly-accessible URL on the Helix community site (does anyone actually use Helix ?) that contains a bunch of specifications for RealVideo 8 and 9. I have been sifting through the documents to see exactly what they contain as the different files seem to be higher revisions of the same documents. Here is the title, date, and version of each PDF document :

  • RNDecoderPerformanceARM.pdf : Decoder Performance on StrongARM and XScale ; May 12, 2003 ; Version 1.1
  • rv89_decoder_summary.pdf : RealVideo 8/9 Combo Decoder Summary ; October 23, 2002 ; Version 1.0
  • rv9_dec_external_spec_v14.pdf : RealVideo 9 External Specification ; November 7, 2003 ; Version 1.4
  • rv8_dec_external_spec_v20.pdf : RealVideo 8 External Specification ; September 19, 2002 ; Version 2.0
  • RV8DecoderExternalSpecificationv201.pdf : RealVideo 8 External Specification ; October 20, 2006 ; Version 2.01
  • RV8DecoderExternalSpecificationv202.pdf : RealVideo 8 External Specification ; April 23, 2007 ; Version 2.02
  • RV8DecoderExternalSpecificationv203.pdf : RealVideo 8 External Specification ; July 20, 2007 ; Version 2.03
  • RV8DecoderExternalSpecificationv21.pdf : RealVideo 8 External Specification ; September 11, 2007 ; Version 2.1
  • RV9DecoderExternalSpecificationv15.pdf ; RealVideo 9 External Specification ; January 26, 2002 ; Version 1.5
  • RV9DecoderExternalSpecificationv16.pdf ; RealVideo 9 External Specification ; August 17, 2005 ; Version 1.6
  • RV9DecoderExternalSpecificationv18.pdf ; RealVideo 9 External Specification ; September 11, 2007 ; Version 1.8

  Additionally, there is an Excel spreadsheet entitled realvideo-faq.xls that appears to contain some general tech support advice for using Real’s official code. There are also 3 ZIP archives which contain profiling information about the official source code (post processing and entropy decoding top the charts which is no big surprise).

  I guess the latest version of each document (the ones dated September 11, 2007) are worth mirroring. Unfortunately, those latest document versions use a terrible font.

• lavu/tx : optimize and simplify inverse MDCTs

  15 août 2022, par Lynne

  lavu/tx : optimize and simplify inverse MDCTs
  Convert the input from a scatter to a gather instead,
  
  which is faster and better for SIMD.
  
  Also, add a pre-shuffled exptab version to avoid
  
  gathering there at all. This doubles the exptab size,
  
  but the speedup makes it worth it. In SIMD, the
  
  exptab will likely be purged to a higher cache
  
  anyway because of the FFT in the middle, and
  
  the amount of loads stays identical.
  For a 960-point inverse MDCT, the speedup is 10%.
  This makes it possible to write sane and fast SIMD
  
  versions of inverse MDCTs.
  

  • [DH] libavutil/tx.c
  • [DH] libavutil/tx_priv.h
  • [DH] libavutil/tx_template.c