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（更人性化）的实时进度。

这是我用来捕获子进程输出的代码：

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”完美结合。

但是，当我切换到“x265”命令时，事情就变成了有线。

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"，理论上，它应该按时间顺序给出以下输出：

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

但事实是，中间那些指示实时进度的输出块不会被捕获到它更新的每一个特定的部分。 popen.stdout.readline() 命令将被阻止，直到进度达到 100%，然后完全输出。显然这不是我想要的。

（↓我指的是这部分）

[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   

谁能帮我弄清楚发生了什么以及如何解决它以实现我的目标？

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，因此末尾没有换行符，而是输出只有一个回车符以将光标返回到同一行的开头并覆盖上一行。所以使用 readline 不会达到你想要的。您必须编写自己的自定义逻辑来读取输出并将输出拆分为行。

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)