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• how to convert wav file to mp3 frame by frame by using ffmpeg in python

  23 août 2016, par Mehrdad Dadvand

  i am trying to code something like VOIP in python. i use pyaudio to record voice and send these frames to another computer through socket. but the size of each frame is much more than mp3 frames.
  so i have decided to covert these frame to mp3 before send them. i think ffmpeg is good choice to convert these frames. but as far as i know ffmpeg inputs are files not frames.
  is there any way to convert these frames to mp3 frame by frame in python ?
  is there any other library that relates to this conversion ?

• Revision 72c5778ec5 : Added two new skip experiments. sf->unused_mode_skip_lvl. Tests modes as normal

  1er juillet 2013, par Paul Wilkins

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

  
   Modify /vp9/encoder/vp9_onyx_if.c

  
   Modify /vp9/encoder/vp9_onyx_int.h

  
   Modify /vp9/encoder/vp9_rdopt.c

  
  
  Added two new skip experiments.

  sf->unused_mode_skip_lvl. Tests modes as normal for all
  sizes at or below the given level. At larger sizes it skips
  all modes that were not chosen at any smaller size.
  Hence setting BLOCK_SIZE_SB64X64 is in effect off.
  Setting BLOCK_SIZE_AB4X4 will only consider modes that
  were chosen for one or more 4x4 blocks at larger sizes.

  sf->reference_masking.
  Do a test encode of the NONE partition at one size and create
  a reference frame mask based on the best rd choice. In the
  full search only allow this reference frame.
  Currently it is testing 64x64 and repeats this in the full search.
  This does not work well with Jim's Partition code just now and
  is disabled by default.

  Change-Id : I8f8c52d2ef4a0c08100150b0ea4155d1aaab93dd

• Making Sure The PNG Gets There

  14 juin 2013, par Multimedia Mike — General

  Rewind to 1999. I was developing an HTTP-based remote management interface for an embedded device. The device sat on an ethernet LAN and you could point a web browser at it. The pitch was to transmit an image of the device’s touch screen and the user could click on the picture to interact with the device. So we needed an image format. If you were computing at the time, you know that the web was insufferably limited back then. Our choice basically came down to GIF and JPEG. Being the office’s annoying free software zealot, I was championing a little known up and coming format named PNG.

  So the challenge was to create our own PNG encoder (incorporating a library like libpng wasn’t an option for this platform). I seem to remember being annoyed at having to implement an integrity check (CRC) for the PNG encoder. It’s part of the PNG spec, after all. It just seemed so redundant. At the time, I reasoned that there were 5 layers of integrity validation in play.

  I don’t know why, but I was reflecting on this episode recently and decided to revisit it. Here are all the encapsulation layers of a PNG file when flung over an ethernet network :

  
  
  

  So there are up to 5 encapsulations for the data in this situation. At the innermost level is the image data which is compressed with the zlib DEFLATE method. At first, I thought that this also had a CRC or checksum. However, in researching this post, I couldn’t find any evidence of such an integrity check. Further, I don’t think we bothered to compress the PNG data in this project long ago. It was a small image, monochrome, and transferring via LAN, so the encoder could get away with signaling uncompressed data.

  The graphical data gets wrapped up in a PNG chunk and all PNG chunks have a CRC. To transmit via the network, it goes into a TCP frame, which also has a checksum. That goes into an IP packet. I previously believed that this represented another integrity check. While an IP frame does have a checksum, the checksum only covers the IP header and not the payload. So that doesn’t really count towards this goal.

  Finally, the data gets encapsulated into an ethernet frame which has — you guessed it — a CRC.

  I see that other link layer protocols like PPP and wireless ethernet (802.11) also feature frame CRCs. So I guess what I’m saying is that, if you transfer a PNG file over the network, you can be confident that the data will be free of any errors.