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• avcodec/h264_refs : Rewrite code to make control flow clearer

  26 mars 2024, par Andreas Rheinhardt

  avcodec/h264_refs : Rewrite code to make control flow clearer
  While this change IMO makes the control flow clearer
  
  for the human reader, it is especially important for
  
  GCC : It erroneously believes that it is possible to
  
  enter the SHORT2(UNUSED|LONG) cases without having
  
  entered the preceding block that initializes pic,
  
  frame_num, structure and j ; it would emit -Wmaybe-uninitialized
  
  warnings for these variables if they were not pseudo-
  
  initialized with av_uninit(). This patch allows to remove
  
  the latter.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] libavcodec/h264_refs.c

• twinvq : move all bitstream reading into single place

  4 août 2013, par Kostya Shishkov

  twinvq : move all bitstream reading into single place
  This is required for the future addition of VoxWare MetaSound decoder, for its
  
  functions are mostly the same but bitstream reader is completely different
  
  and bitstream format is slightly different too.
  Signed-off-by : Diego Biurrun <diego@biurrun.de>
  

  • [DBH] libavcodec/twinvq.c

• Read portion of lines from child process in Rust (chunk of data)

  2 octobre 2022, par Alexey Volodko

  When I try to spawn a child ffmpeg process I use additonal flag -progress, next I use pipe to pass this progress output to the stderr.
So the whole command looks like :

  


  ffmpeg -i ... -progress pipe:2 ...


  


  Without -progress flag ffmepg outputs following line in stderr, probably once per second :

  


  frame=46 46 fps=0.0 q=0.0 size=       0kB time=00:00:01.72 bitrate=   0.2kbits/s speed=2.69x


  


  With -progress flag ffmepg outputs (multiple lines) in stderr, probably once per second :

  


  frame=1   1 fps=0.0 q=0.0 size=       0kB time=00:00:00.19 bitrate=   2.0kbits/s speed=2.94x    
fps=0.00
stream_0_0_q=0.0
bitrate=   2.0kbits/s
total_size=48
out_time_us=192000
out_time_ms=192000
out_time=00:00:00.192000
dup_frames=0
drop_frames=0
speed=2.94x
progress=continue


  


  The main puppose of using -progress flag is to calc percentage of completion by parsing out_time_ms line and comparing to the whole duration.

  


  Reading this chunk (portion of lines) is pretty simple in NodeJS :

  


  const { spawn } = require('child_process');
const child = spawn('ffmpeg', [..., '-progress', 'pipe:2', ...]);

child.stderr.on('data', (data) => {
  // data will contain multiple lines, exactly one chunk
});


  


  Reading this chunk (portion of lines) is pretty simple in Deno also :

  


  const child = Deno.spawnChild("ffmpeg", {
  args: [..., '-progress', 'pipe:2', ...],
});
const stderrReader = child.stderr.getReader();
let readResult = await stderrReader.read();
while (readResult.done !== true) {
  readResult = await stderrReader.read();
  // readResult will contain multiple lines, exactly one chunk
}


  


  I can't achieve the same in rust :

  


  let mut command = Command::new("ffmpeg");
command.args(["...", "-progress", "pipe:2", "..."]);
let mut child = command
  .stdout(Stdio::piped())
  .stderr(Stdio::piped())
  .spawn()
  .unwrap();

let child_stderr = child.stderr.as_mut().expect("Unable to pipe stderr");
let mut reader = BufReader::new(child_stderr);
let mut buff = String::new();
while reader.read_line(&mut buff).expect("Unable to read chunk") > 0 {
  // buff will contain only on line
  buff.clear();
}


  


  I am new in Rust. I can not detect what character signals end of chunk.

  


  

  • Runnig read_line() - will read only one line.

  


  • Runnig read_to_end() - will read the whole output until the end of process (EOF).

  


  


  How can I read in Rust portion of lines that ffmpeg outputs probably once per second ?
How Node/Deno detects this "end of chunk" ?
Does rust have such event/signal also ?