如何使用Python捕获x265.exe的实时命令行输出？

Question

我想为x265.exe编写一个GUI，它提供了更好的（更人性化的）实时进度。

这是我用来捕获子流程输出的代码：

import subprocess

cmd = r'ping www.baidu.com -n 4'
popen = subprocess.Popen(cmd, stdout = subprocess.PIPE ,stderr=subprocess.STDOUT ,shell=True)
while True:
    next_line = popen.stdout.readline()
    if next_line == b'' and popen.poll() != None:
        break
    else:
        print(next_line.decode('ascii').replace('\r\n','\n') , end='')

它与'ping'完美配合​​。

但是，当我使用'x265'命令时，一切都已完成。

例如，如果我在前面的代码中将字符串变量'cmd'替换为"x265 --y4m --crf 21 --output output.hevc input.y4m"。从理论上讲，它应该按时间顺序排列以下输出：

y4m  [info]: 1920x1080 fps 24000/1001 i420p10 frames 0 - 100 of 101
x265 [info]: Using preset ultrafast & tune none
raw  [info]: output file: C:\temp\output.hevc
x265 [info]: Main 10 profile, Level-4 (Main tier)
x265 [info]: Thread pool created using 16 threads
x265 [info]: Slices                              : 1
x265 [info]: frame threads / pool features       : 4 / wpp(34 rows)
x265 [info]: Coding QT: max CU size, min CU size : 32 / 16
x265 [info]: Residual QT: max TU size, max depth : 32 / 1 inter / 1 intra
x265 [info]: ME / range / subpel / merge         : dia / 57 / 0 / 2
x265 [info]: Keyframe min / max / scenecut / bias: 23 / 250 / 0 / 5.00
x265 [info]: Lookahead / bframes / badapt        : 5 / 3 / 0
x265 [info]: AQ: mode / str / qg-size / cu-tree  : 1 / 0.0 / 32 / 1
x265 [info]: Rate Control / qCompress            : CRF-21.0 / 0.60
x265 [info]: tools: strong-intra-smoothing lslices=6 deblock

[1.0%] 1/101 frames, 6.289 fps, 7217.8 kb/s
[25.7%] 26/101 frames, 59.23 fps, 299.23 kb/s
[45.5%] 46/101 frames, 66.76 fps, 322.81 kb/s  
[69.3%] 70/101 frames, 73.30 fps, 224.53 kb/s
[93.1%] 94/101 frames, 77.05 fps, 173.67 kb/s   

x265 [info]: frame I:      1, Avg QP:23.45  kb/s: 7098.44 
x265 [info]: frame P:     25, Avg QP:25.71  kb/s: 311.24  
x265 [info]: frame B:     75, Avg QP:28.33  kb/s: 23.89   
x265 [info]: consecutive B-frames: 3.8% 0.0% 0.0% 96.2% 

encoded 101 frames in 1.22s (82.58 fps), 165.06 kb/s, Avg QP:27.64

但是事实是，中间部分的那些表示实时进度的输出块不会在每次更新时捕获。 popen.stdout.readline()命令将被阻止，直到进度达到100％，然后完全输出。显然那不是我想要的。

（↓是指这个部分）

[1.0%] 1/101 frames, 6.289 fps, 7217.8 kb/s
[25.7%] 26/101 frames, 59.23 fps, 299.23 kb/s
[45.5%] 46/101 frames, 66.76 fps, 322.81 kb/s  
[69.3%] 70/101 frames, 73.30 fps, 224.53 kb/s
[93.1%] 94/101 frames, 77.05 fps, 173.67 kb/s   

任何人都可以帮助我了解正在发生的事情以及如何解决它以实现我的目标吗？

非常感谢。

Answer 1

我的猜测是，由于命令输出正在就地更新文本，所以末尾没有换行符，相反，输出仅具有回车符以在同一行的开头返回光标，并且覆盖前一行。因此，使用readline将无法实现您想要的。您将必须编写自己的自定义逻辑来读取输出并将输出分成几行。

以下是我的实现

import re
import subprocess

cmd = r'ping www.baidu.com -n 4'
popen = subprocess.Popen(cmd, stdout = subprocess.PIPE ,stderr=subprocess.STDOUT ,shell=True)

read_chunk_size = 20
next_lines = ['']
while True:
    # read the stdout upto read_chunk_size bytes
    chunk = popen.stdout.read(read_chunk_size)
    # checking if process has finished
    if not chunk and popen.poll() != None:
        break
    # splitting the read string of charachters by either \n, \r or \n\r
    split_chunk = re.split('\n|\r|\n\r', chunk.decode('utf-8'))
    # combining the first of the split strings to the last of the strings
    # which were read in the last iteration. since we are reading upto only 
    # a fixed length, we may get incomplete lines
    next_lines = [next_lines[-1] + split_chunk[0]] + split_chunk[1:]
    # iterate upto the second last item in next_lines, since the last item may
    # still be incomplete which will be read in the next iteration
    for line in next_lines[:-1]:
        # read your lines here
        print(line)