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• aacenc : implement Intensity Stereo encoding support

  2 juillet 2015, par Rostislav Pehlivanov

  aacenc : implement Intensity Stereo encoding support
  This commit implements intensity stereo coding support
  
  to the native aac encoder. This is a way to increase the efficiency
  
  of the encoder by zeroing the right channel’s spectral coefficients
  
  (in a channel pair) and rederiving them in the decoder using information
  
  from the scalefactor indices of special band types. This commit
  
  confomrs to the official ISO 13818-7 specifications, although due to
  
  their ambiguity certain deviations have been taken to ensure maximum
  
  sound quality. This commit has been extensively tested and has shown
  
  to not result in audiable audio artifacts unless in extreme cases.
  
  This commit also adds an option, aac_is, which has the value of
  
  0 by default. Intensity Stereo is part of the scalable aac profile
  
  and is thus non-default.
  The way IS coding works is that it rederives the right channel’s
  
  spectral coefficients from the left channel via the scalefactor
  
  index values left in the right channel. Since an entire band’s
  
  spectral coefficients do not need to be coded, the encoder’s
  
  efficiency jumps up and it unzeroes some high frequency values
  
  which it previously did not have enough bits to encode. That way
  
  less information is lost than the information lost by rederiving
  
  the spectral coefficients with some error. This is why the
  
  filesize of files encoded with IS do not decrease significantly.
  
  Users wishing that IS coding should reduce filesize are expected
  
  to reduce their encoding bitrates appropriately.
  This is V2 of the commit. The old version did not mark ms_mask as
  
  0 since M/S and IS coding are incompactible, which resulted in
  
  distortions with M/S coding enabled. This version also improves
  
  phase detection by measuring it for every spectral coefficient in
  
  the band and using a simple majority rule to determine whether the
  
  coefficients are in or out of phase. Also, the energy values per
  
  spectral coefficient were changed as to reflect the
  
  official specifications.
  Reviewed-by : Claudio Freire <klaussfreire@gmail.com>
  
  Signed-off-by : Michael Niedermayer <michaelni@gmx.at>
  

  • [DH] libavcodec/aaccoder.c
  • [DH] libavcodec/aacenc.c
  • [DH] libavcodec/aacenc.h

• How to trigger from button in UVC camera

  8 août 2016, par Buddhishan Manamperi

  I’m taking pictures from a webcam using Intel Edison. I was able to capture still images from the camera after installing uvc driver for linux and ffmpeg software. I use a script to capture.

  ./ffmpeg -s 640x640 -f video4linux2 -i /dev/video0 -vframes 1 image.jpeg;

  I want to capture the image from the button (in the web cam) press event. I used a USB analyzer in windows to analyze packets. It was found that URB_FUNCTION_BULK_OR_INTERRUPT_TRANSFER is transferring UP and DOWN when the button is pressed.

  Please Help me to implement button press triggering on Linux so that I could use it on Edison.

• Revision 34251 : Sortons STEP de la steppe... Ce nom n’est pas définitif. Pour l’instant il ...

  7 janvier 2010, par marcimat@… — Log

  Sortons STEP de la steppe...
  Ce nom n’est pas définitif. Pour l’instant il signifie « Système de téléchargement de plugins »
  Ce plugin a pour vocation de faciliter la recherche, l’installation et la mise à jour de plugins SPIP. Il fonctionne -actuellement- avec SPIP 2.0.10 et PHP5 (pour scandir)
  Il n’est pas terminé et est en phase de développement encore.
  Aucune mise à jour de sa base de donnée ne sera effectuée avant une version de test (i.e si le plugin se met à planter suite à une mise à jour, il faut le désinstaller et le réactiver).
  Ce plugin se veut être (pour l’instant) comme une sorte de "Synaptic" pour SPIP (pour ceux qui connaissent Ubuntu) en un tout petit peu plus convivial.

  ---

  Lire le fichier TODO pour la liste des taches à réaliser.