问题描述
我有一个已转换为 4D NumPy 数组的视频 (test.mkv
) -(帧、高度、宽度、颜色通道)。我什至设法将该数组转换回相同的视频 (test_2.mkv
),而无需更改任何内容。但是,在将这个新的 test_2.mkv
读回新的 NumPy 数组后,第一个视频的数组与第二个视频的数组不同,即它们的哈希不匹配,numpy.array_equal()
函数返回 false .我曾尝试同时使用 python-ffmpeg 和 scikit-video,但无法让数组匹配。
Python-ffmpeg 尝试:
import ffmpeg
import numpy as np
import hashlib
file_name = 'test.mkv'
# Get video dimensions and framerate
probe = ffmpeg.probe(file_name)
video_stream = next((stream for stream in probe['streams'] if stream['codec_type'] == 'video'),None)
width = int(video_stream['width'])
height = int(video_stream['height'])
frame_rate = video_stream['avg_frame_rate']
# Read video into buffer
out,error = (
ffmpeg
.input(file_name,threads=120)
.output("pipe:",format='rawvideo',pix_fmt='rgb24')
.run(capture_stdout=True)
)
# Convert video buffer to array
video = (
np
.frombuffer(out,np.uint8)
.reshape([-1,height,width,3])
)
# Convert array to buffer
video_buffer = (
np.ndarray
.flatten(video)
.tobytes()
)
# Write buffer back into a video
process = (
ffmpeg
.input('pipe:',s='{}x{}'.format(width,height))
.output("test_2.mkv",r=frame_rate)
.overwrite_output()
.run_async(pipe_stdin=True)
)
process.communicate(input=video_buffer)
# Read the newly written video
out_2,error = (
ffmpeg
.input("test_2.mkv",threads=40)
.output("pipe:",pix_fmt='rgb24')
.run(capture_stdout=True)
)
# Convert new video into array
video_2 = (
np
.frombuffer(out_2,3])
)
# Video dimesions change
print(f'{video.shape} vs {video_2.shape}') # (844,1080,608,3) vs (2025,3)
print(f'{np.array_equal(video,video_2)}') # False
# Hashes don't match
print(hashlib.sha256(bytes(video_2)).digest()) # b'\x88\x00\xc8\x0ed\x84!\x01\x9e\x08 \xd0U\x9a(\x02\x0b-\xeeA\xecU\xf7\xad0xa\x9e\\\xbck\xc3'
print(hashlib.sha256(bytes(video)).digest()) # b'\x9d\xc1\x07xh\x1b\x04I\xed\x906\xe57\xba\xf3\xf1k\x08\xfa\xf1\xfaM\x9a\xcf\xa9\t8\xf0\xc9\t\xa9\xb7'
Scikit 视频尝试:
import skvideo.io as sk
import numpy as np
video_data = sk.vread('test.mkv')
sk.vwrite('test_2_ski.mkv',video_data)
video_data_2 = sk.vread('test_2_ski.mkv')
# Dimensions match but...
print(video_data.shape) # (844,3)
print(video_data_2.shape) # (844,3)
# ...array elements don't
print(np.array_equal(video_data,video_data_2)) # False
# Hashes don't match either
print(hashlib.sha256(bytes(video_2)).digest()) # b'\x8b?]\x8epD:\xd9B\x14\xc7\xba\xect\x15G\xfaRP\xde\xad&EC\x15\xc3\x07\n{a[\x80'
print(hashlib.sha256(bytes(video)).digest()) # b'\x9d\xc1\x07xh\x1b\x04I\xed\x906\xe57\xba\xf3\xf1k\x08\xfa\xf1\xfaM\x9a\xcf\xa9\t8\xf0\xc9\t\xa9\xb7'
我不明白我哪里出错了,两个各自的文档都没有强调如何完成这个特定的任务。任何帮助表示赞赏。谢谢。
解决方法
在写入和读取视频文件时需要仔细注意获得相同的哈希值。
在比较hash之前,先试试看视频。
我建议进行以下修改:
- 使用 AVI 容器(而不是 MKV)以原始视频格式存储
test_2
视频。
AVI 视频容器最初是为存储原始视频而设计的。
可能有一种方法可以在 MKV 容器中存储原始或无损 RGB 视频,但我不知道有这样的选项。 - 设置
test_2
视频的输入像素格式。
添加参数:pixel_format='rgb24'
.
注意:我将其修改为pixel_format='bgr24'
,因为 AVI 支持bgr24
而不是rgb24
。 - 选择视频为
test_2
视频的无损编解码器。
您可以选择vcodec='rawvideo'
(AVI 支持原始视频编解码器,但 MKV 不支持)。
注意:
为了获得相等的哈希值,您需要寻找支持rgb24
(或bgr24
)像素格式的无损视频编解码器。
大多数无损编解码器,将像素格式从 RGB 转换为 YUV。
RGB 到 YUV 的转换有舍入错误,阻止了相等的散列。
(我想有办法绕过它,但它有点复杂)。
以下是经过少量修改的完整代码:
import ffmpeg
import numpy as np
import hashlib
file_name = 'test.mkv'
# Get video dimensions and framerate
probe = ffmpeg.probe(file_name)
video_stream = next((stream for stream in probe['streams'] if stream['codec_type'] == 'video'),None)
width = int(video_stream['width'])
height = int(video_stream['height'])
frame_rate = video_stream['avg_frame_rate']
# Read video into buffer
out,error = (
ffmpeg
.input(file_name,threads=120)
.output("pipe:",format='rawvideo',pix_fmt='bgr24') # Select bgr24 instead of rgb24 (becasue raw AVI requires bgr24).
.run(capture_stdout=True)
)
# Convert video buffer to array
video = (
np
.frombuffer(out,np.uint8)
.reshape([-1,height,width,3])
)
# Convert array to buffer
video_buffer = (
np.ndarray
.flatten(video)
.tobytes()
)
# Write buffer back into a video
process = (
ffmpeg
.input('pipe:',s='{}x{}'.format(width,height),pixel_format='bgr24',r=frame_rate) # Set input pixel format.
.output("test_2.avi",vcodec='rawvideo') # Select video code "rawvideo"
.overwrite_output()
.run_async(pipe_stdin=True)
)
process.communicate(input=video_buffer)
# Read the newly written video
out_2,error = (
ffmpeg
.input("test_2.avi",threads=40)
.output("pipe:",pix_fmt='bgr24')
.run(capture_stdout=True)
)
# Convert new video into array
video_2 = (
np
.frombuffer(out_2,3])
)
# Video dimesions change
print(f'{video.shape} vs {video_2.shape}') # (844,1080,608,3) vs (844,3)
print(f'{np.array_equal(video,video_2)}') # True
# Hashes do match
print(hashlib.sha256(bytes(video_2)).digest())
print(hashlib.sha256(bytes(video)).digest())
结果(相同的哈希值):
True
b"\xd1yy\x97\x8e\xce\x13\xbcI#\xd2PMP\x80(i+5\xe1\xcd\xab\xf3f\xbe\xcd\xd5'\xbaq\xdd\x9b"
b"\xd1yy\x97\x8e\xce\x13\xbcI#\xd2PMP\x80(i+5\xe1\xcd\xab\xf3f\xbe\xcd\xd5'\xbaq\xdd\x9b"
更新:
使用 ffv1 编码器:
使用 .mkv 的 ffv1 编码器实现相同的散列
- 在
vcodec='ffv1'
的参数中选择output()
。
还有一件事:
-
将参数
r=frame_rate
从输出参数移动到输入参数。
这不直观……但是当从帧中创建视频时,应将帧速率定义为输入的参数。# Write buffer back into a video process = ( ffmpeg .input('pipe:',pixel_format='rgb24',r=frame_rate) # Set input pixel format. .output("test_2.mkv",vcodec='ffv1') # Select video code "rawvideo" .overwrite_output() .run_async(pipe_stdin=True) )
这是完整的代码示例:
import ffmpeg
import numpy as np
import hashlib
file_name = 'test.mkv'
# Get video dimensions and framerate
probe = ffmpeg.probe(file_name)
video_stream = next((stream for stream in probe['streams'] if stream['codec_type'] == 'video'),pix_fmt='rgb24') # Select rgb24 instead of rgb24 (becasue raw AVI requires rgb24).
.run(capture_stdout=True)
)
# Convert video buffer to array
video = (
np
.frombuffer(out,r=frame_rate) # Set input pixel format.
.output("test_2.mkv",vcodec='ffv1') # Select video code "rawvideo"
.overwrite_output()
.run_async(pipe_stdin=True)
)
process.communicate(input=video_buffer)
# Read the newly written video
out_2,error = (
ffmpeg
.input("test_2.mkv",pix_fmt='rgb24')
.run(capture_stdout=True)
)
# Convert new video into array
video_2 = (
np
.frombuffer(out_2,video_2)}') # True
# Hashes do match
print(hashlib.sha256(bytes(video_2)).digest())
print(hashlib.sha256(bytes(video)).digest())
结果(相同的哈希值,使用您的输入文件):
True
b'\x9d\xc1\x07xh\x1b\x04I\xed\x906\xe57\xba\xf3\xf1k\x08\xfa\xf1\xfaM\x9a\xcf\xa9\t8\xf0\xc9\t\xa9\xb7'
b'\x9d\xc1\x07xh\x1b\x04I\xed\x906\xe57\xba\xf3\xf1k\x08\xfa\xf1\xfaM\x9a\xcf\xa9\t8\xf0\xc9\t\xa9\xb7'
更新:
使用 Scikit-Video:
以下代码示例使用 Scikit-Video。
如果不使用 ffv1
,我找不到选择 skvideo.io.FFmpegWriter
编解码器的方法。
该实现使用 for 循环逐帧写入视频。
import skvideo.io as sk
import numpy as np
import hashlib
video_data = sk.vread('test.mkv')
# Create FFmpeg vidoe writer
writer = sk.FFmpegWriter('test_2_ski.mkv',outputdict={'-vcodec': 'ffv1' })
#sk.vwrite('test_2_ski.mkv',video_data)
# Write frame by frame in a loop
for i in range(video_data.shape[0]):
writer.writeFrame(video_data[i,:,:])
writer.close() # Close video writer.
video_data_2 = sk.vread('test_2_ski.mkv')
# Dimensions match
print(video_data.shape) # (844,3)
print(video_data_2.shape) # (844,3)
# Array elements match
print(np.array_equal(video_data,video_data_2))
# Hashes match
print(hashlib.sha256(bytes(video_data_2)).digest())
print(hashlib.sha256(bytes(video_data)).digest())