提取帧失败：处理输入时发现无效数据
Extracting frame fails with: Invalid data found when processing input
我有以下创建虚拟视频文件的方法：
def create_dummy_mp4_video() -> None:
cmd = (
f"ffmpeg -y " # rewrite if exists
f"-f lavfi -i color=size=100x100:rate=10:color=black " # blank video
f"-f lavfi -i anullsrc=channel_layout=stereo:sample_rate=44100 " # silent audio
f"-t 1 " # video duration, seconds
"output.mp4" # file name
)
proc = subprocess.run(
shlex.split(cmd),
stdout=subprocess.PIPE,
stderr=subprocess.PIPE,
shell=False,
)
if proc.returncode != 0:
raise Exception()
@dataclass(frozen=True)
class FakeVideo:
body: bytes
width: int
height: int
fps: int
size: int
frames: int
length_s: int
def video() -> FakeVideo:
w, h, fps, sec, filename = 100, 100, 10, 1, "output.mp4"
create_dummy_mp4_video()
video_path = os.path.join(os.getcwd(), filename)
with open(video_path, "rb") as file:
body = file.read()
size = len(body)
frames = fps // sec
return FakeVideo(
body=body, width=w, height=h, fps=fps,
size=size, frames=frames, length_s=sec,
)
然后我想在特定时间提取一帧，我是这样做的：
async def run_shell_command(frame_millisecond, data: bytes) -> bytes:
async with aiofiles.tempfile.NamedTemporaryFile("wb") as file:
await file.write(data)
proc = await asyncio.create_subprocess_exec(
"ffmpeg",
"-i",
file.name,
"-ss",
f"{frame_millisecond}ms", # seek the position to the specific millisecond
"-vframes", "1", # only handle one video frame
"-c:v", "png", # select the output encoder
"-f", "image2pipe", "-", # force output file to stdout,
stdout=asyncio.subprocess.PIPE,
stderr=asyncio.subprocess.PIPE,
)
stdout, stderr = await proc.communicate()
level = logging.DEBUG if proc.returncode == 0 else logging.WARN
LOGGER.log(level, f"[cmd exited with {proc.returncode}]")
if stderr:
print(level, f"[stderr]{stderr.decode()}")
LOGGER.log(level, f"[stderr]{stderr.decode()}")
return stdout
async def runner():
v = video()
time = int(v.length_s / 2 * 1000)
res = await run_shell_command(time, v.body)
assert isinstance(res, bytes)
assert imghdr.what(h=res, file=None) == "png"
loop = asyncio.get_event_loop()
loop.run_until_complete(runner())
此代码失败并出现以下错误：
/tmp/tmpzo786lfg: Invalid data found when processing input
请帮忙找出我代码中的问题。
在调查过程中，我发现如果我像这样更改视频的大小，它会起作用：
f"-f lavfi -i color=size=1280x720:rate=25:color=black " # blank video
但我希望能够处理任何视频。
我用的是ffmpg 4.3.3-0+deb11u1
看来你必须确保在执行 FFmpeg 之前将数据写入临时文件。
我对 asyncio 和 aiofiles 没有任何经验，我是 运行 Windows 10，所以我不确定 Linux 行为...
我试着在file.write(data)后面加上await file.flush()，但是FFmpeg执行结果是“Permission denied”。
我使用以下 post 中的解决方案解决了它：
将 delete=False 参数添加到 tempfile.NamedTemporaryFile:
async with aiofiles.tempfile.NamedTemporaryFile("wb", delete=False) as file:
在await file.write(data)之后添加await file.close()。
关闭文件用于确保所有数据都写入文件，然后再执行 FFmpeg。
在return stdout前添加os.unlink(file.name)。
完整代码：
import subprocess
import asyncio
from dataclasses import dataclass
import shlex
import aiofiles
import os
import logging
import imghdr
def create_dummy_mp4_video() -> None:
cmd = (
f"ffmpeg -y " # rewrite if exists
f"-f lavfi -i color=size=100x100:rate=10:color=black " # blank video
f"-f lavfi -i anullsrc=channel_layout=stereo:sample_rate=44100 " # silent audio
f"-t 1 " # video duration, seconds
"output.mp4" # file name
)
proc = subprocess.run(
shlex.split(cmd),
stdout=subprocess.PIPE,
stderr=subprocess.DEVNULL, #stderr=subprocess.PIPE,
shell=False,
)
if proc.returncode != 0:
raise Exception()
@dataclass(frozen=True)
class FakeVideo:
body: bytes
width: int
height: int
fps: int
size: int
frames: int
length_s: int
def video() -> FakeVideo:
w, h, fps, sec, filename = 100, 100, 10, 1, "output.mp4"
create_dummy_mp4_video()
video_path = os.path.join(os.getcwd(), filename)
with open(video_path, "rb") as file:
body = file.read()
size = len(body)
frames = fps // sec
return FakeVideo(
body=body, width=w, height=h, fps=fps,
size=size, frames=frames, length_s=sec,
)
async def run_shell_command(frame_millisecond, data: bytes) -> bytes:
#
async with aiofiles.tempfile.NamedTemporaryFile("wb", delete=False) as file:
await file.write(data)
#await file.flush() # Flush data to file before executing FFmpeg ?
await file.close() # Close the file before executing FFmpeg.
proc = await asyncio.create_subprocess_exec(
"ffmpeg",
"-i",
file.name,
"-ss",
f"{frame_millisecond}ms", # seek the position to the specific millisecond
"-vframes", "1", # only handle one video frame
"-c:v", "png", # select the output encoder
"-f", "image2pipe", "-", # force output file to stdout,
stdout=asyncio.subprocess.PIPE,
stderr=asyncio.subprocess.PIPE
)
stdout, stderr = await proc.communicate()
level = logging.DEBUG if proc.returncode == 0 else logging.WARN
#LOGGER.log(level, f"[cmd exited with {proc.returncode}]")
if stderr:
print(level, f"[stderr]{stderr.decode()}")
#LOGGER.log(level, f"[stderr]{stderr.decode()}")
os.unlink(file.name) # Unlink is required because delete=False was used
return stdout
async def runner():
v = video()
time = int(v.length_s / 2 * 1000)
res = await run_shell_command(time, v.body)
assert isinstance(res, bytes)
assert imghdr.what(h=res, file=None) == "png"
loop = asyncio.get_event_loop()
loop.run_until_complete(runner())
备注：
- 我删除了
LOGGER 因为找不到 LOGGER 模块。
- 下次，请将所有导入添加到您发布的代码中（找到它们并非易事）。
我有以下创建虚拟视频文件的方法：
def create_dummy_mp4_video() -> None:
cmd = (
f"ffmpeg -y " # rewrite if exists
f"-f lavfi -i color=size=100x100:rate=10:color=black " # blank video
f"-f lavfi -i anullsrc=channel_layout=stereo:sample_rate=44100 " # silent audio
f"-t 1 " # video duration, seconds
"output.mp4" # file name
)
proc = subprocess.run(
shlex.split(cmd),
stdout=subprocess.PIPE,
stderr=subprocess.PIPE,
shell=False,
)
if proc.returncode != 0:
raise Exception()
@dataclass(frozen=True)
class FakeVideo:
body: bytes
width: int
height: int
fps: int
size: int
frames: int
length_s: int
def video() -> FakeVideo:
w, h, fps, sec, filename = 100, 100, 10, 1, "output.mp4"
create_dummy_mp4_video()
video_path = os.path.join(os.getcwd(), filename)
with open(video_path, "rb") as file:
body = file.read()
size = len(body)
frames = fps // sec
return FakeVideo(
body=body, width=w, height=h, fps=fps,
size=size, frames=frames, length_s=sec,
)
然后我想在特定时间提取一帧，我是这样做的：
async def run_shell_command(frame_millisecond, data: bytes) -> bytes:
async with aiofiles.tempfile.NamedTemporaryFile("wb") as file:
await file.write(data)
proc = await asyncio.create_subprocess_exec(
"ffmpeg",
"-i",
file.name,
"-ss",
f"{frame_millisecond}ms", # seek the position to the specific millisecond
"-vframes", "1", # only handle one video frame
"-c:v", "png", # select the output encoder
"-f", "image2pipe", "-", # force output file to stdout,
stdout=asyncio.subprocess.PIPE,
stderr=asyncio.subprocess.PIPE,
)
stdout, stderr = await proc.communicate()
level = logging.DEBUG if proc.returncode == 0 else logging.WARN
LOGGER.log(level, f"[cmd exited with {proc.returncode}]")
if stderr:
print(level, f"[stderr]{stderr.decode()}")
LOGGER.log(level, f"[stderr]{stderr.decode()}")
return stdout
async def runner():
v = video()
time = int(v.length_s / 2 * 1000)
res = await run_shell_command(time, v.body)
assert isinstance(res, bytes)
assert imghdr.what(h=res, file=None) == "png"
loop = asyncio.get_event_loop()
loop.run_until_complete(runner())
此代码失败并出现以下错误：
/tmp/tmpzo786lfg: Invalid data found when processing input
请帮忙找出我代码中的问题。 在调查过程中，我发现如果我像这样更改视频的大小，它会起作用：
f"-f lavfi -i color=size=1280x720:rate=25:color=black " # blank video
但我希望能够处理任何视频。
我用的是ffmpg 4.3.3-0+deb11u1
看来你必须确保在执行 FFmpeg 之前将数据写入临时文件。
我对 asyncio 和 aiofiles 没有任何经验，我是 运行 Windows 10，所以我不确定 Linux 行为...
我试着在file.write(data)后面加上await file.flush()，但是FFmpeg执行结果是“Permission denied”。
我使用以下 post 中的解决方案解决了它：
将
delete=False参数添加到tempfile.NamedTemporaryFile:async with aiofiles.tempfile.NamedTemporaryFile("wb", delete=False) as file:在
await file.write(data)之后添加await file.close()。
关闭文件用于确保所有数据都写入文件，然后再执行 FFmpeg。在
return stdout前添加os.unlink(file.name)。
完整代码：
import subprocess
import asyncio
from dataclasses import dataclass
import shlex
import aiofiles
import os
import logging
import imghdr
def create_dummy_mp4_video() -> None:
cmd = (
f"ffmpeg -y " # rewrite if exists
f"-f lavfi -i color=size=100x100:rate=10:color=black " # blank video
f"-f lavfi -i anullsrc=channel_layout=stereo:sample_rate=44100 " # silent audio
f"-t 1 " # video duration, seconds
"output.mp4" # file name
)
proc = subprocess.run(
shlex.split(cmd),
stdout=subprocess.PIPE,
stderr=subprocess.DEVNULL, #stderr=subprocess.PIPE,
shell=False,
)
if proc.returncode != 0:
raise Exception()
@dataclass(frozen=True)
class FakeVideo:
body: bytes
width: int
height: int
fps: int
size: int
frames: int
length_s: int
def video() -> FakeVideo:
w, h, fps, sec, filename = 100, 100, 10, 1, "output.mp4"
create_dummy_mp4_video()
video_path = os.path.join(os.getcwd(), filename)
with open(video_path, "rb") as file:
body = file.read()
size = len(body)
frames = fps // sec
return FakeVideo(
body=body, width=w, height=h, fps=fps,
size=size, frames=frames, length_s=sec,
)
async def run_shell_command(frame_millisecond, data: bytes) -> bytes:
#
async with aiofiles.tempfile.NamedTemporaryFile("wb", delete=False) as file:
await file.write(data)
#await file.flush() # Flush data to file before executing FFmpeg ?
await file.close() # Close the file before executing FFmpeg.
proc = await asyncio.create_subprocess_exec(
"ffmpeg",
"-i",
file.name,
"-ss",
f"{frame_millisecond}ms", # seek the position to the specific millisecond
"-vframes", "1", # only handle one video frame
"-c:v", "png", # select the output encoder
"-f", "image2pipe", "-", # force output file to stdout,
stdout=asyncio.subprocess.PIPE,
stderr=asyncio.subprocess.PIPE
)
stdout, stderr = await proc.communicate()
level = logging.DEBUG if proc.returncode == 0 else logging.WARN
#LOGGER.log(level, f"[cmd exited with {proc.returncode}]")
if stderr:
print(level, f"[stderr]{stderr.decode()}")
#LOGGER.log(level, f"[stderr]{stderr.decode()}")
os.unlink(file.name) # Unlink is required because delete=False was used
return stdout
async def runner():
v = video()
time = int(v.length_s / 2 * 1000)
res = await run_shell_command(time, v.body)
assert isinstance(res, bytes)
assert imghdr.what(h=res, file=None) == "png"
loop = asyncio.get_event_loop()
loop.run_until_complete(runner())
备注：
- 我删除了
LOGGER因为找不到 LOGGER 模块。 - 下次，请将所有导入添加到您发布的代码中（找到它们并非易事）。