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• Merge commit '3303f86467efa99f23c670707f5be094cc9ce547'

  12 octobre 2017, par James Almer

  Merge commit '3303f86467efa99f23c670707f5be094cc9ce547'
  * commit '3303f86467efa99f23c670707f5be094cc9ce547' :
  
    nvenc : Remove qmin and qmax constraints for nvenc vbr
  [10:06:59 CEST] <BtbN> jamrial, 3303f86467 is a no-op. NV_ENC_PARAMS_RC_2_PASS_VBR is a deprecated rc mode(http://git.videolan.org/?p=ffmpeg.git;a=blob;f=compat/nvenc/nvEncodeAPI.h;h=c3a829421282d5f22f82fc285723f13eb660f053;hb=HEAD#l268).
  
  [10:07:14 CEST] <BtbN> And the first hunk with qmin/qmax was applied to ffmpeg quite a while ago already.
  
  [10:07:49 CEST] <BtbN> In a slightly different fashion, but with the same effect
  
  [10:07:58 CEST] <BtbN> Came as a patch from nvidia iirc
  Merged-by : James Almer <jamrial@gmail.com>
  

• FFmpeg 5 C api codec end of stream situation

  11 mars 2023, par Guanyuming He

  I'm new to FFmpeg api programming (I'm using version 5.1) and am learning from the documentation and official examples.

  


  In the documentation page about send/receive encoding and decoding API overview, end of stream situation is discussed briefly :

  


  


  End of stream situations. These require "flushing" (aka draining) the codec, as the codec might buffer multiple frames or packets internally for performance or out of necessity (consider B-frames). This is handled as follows :

  


  


  


  Instead of valid input, send NULL to the avcodec_send_packet() (decoding) or avcodec_send_frame() (encoding) functions. This will enter draining mode.
Call avcodec_receive_frame() (decoding)
or avcodec_receive_packet() (encoding) in a loop until AVERROR_EOF is returned. The functions will not return AVERROR(EAGAIN), unless you forgot to enter draining mode.
Before decoding can be resumed again, the codec has to be reset with avcodec_flush_buffers().

  


  


  As I understand it, when I get AVERROR_EOF, I have reached a special point where I need to drain buffered data from the codec and finally reset the codec with avcodec_flush_buffers(). Without doing it, I cannot continue decoding/encoding.

  


  Then I have some questions :

  


  

  1. If I received EOF when I already finished sending data (e.g. when after EOF is returned by av_read_frame()), how should I tell if it's really finished ?

  


  2. The data returned from the receive_... functions during draining, should I take them as valid ?

  


  


  I might have found answers to those in the official examples, but I'm not sure if the answer is universally true. I noticed that in some official examples, like in transcode_aac.c, draining is only done for the first EOF reached, and then after the second one is received, it is regarded that there are really nothing left. Any data received during draining is also written to the final output.

  


  I just wonder, Is it true for all multimedia files in ffmpeg ?

  


  I appreciate your response and time in advance. :)

  


• How should one start with ffmpeg's API ?

  20 mai 2018, par JoeDough

  I’d like to make a real time streaming program that takes input from a webcamera, ffmpeg looks like a good library for encoding a stream of images but there is no documentation or community tutorials (there is just a doxygen API reference).Where should I start if there’s no official documentation ?