问题
so I do this in my script:
import json
info = json.loads(get_info())
print info
Which outputs:
richard@richard-desktop:~/projects/hello-python$ python main.py
{
"streams": [
{
"index": 0,
"codec_name": "mpeg2video",
"codec_long_name": "MPEG-2 video",
"codec_type": "video",
"codec_time_base": "1001/48000",
"codec_tag_string": "[0][0][0][0]",
"codec_tag": "0x0000",
"width": 1920,
"height": 1080,
"has_b_frames": 1,
"sample_aspect_ratio": "1:1",
"display_aspect_ratio": "16:9",
"pix_fmt": "yuv422p",
"level": 2,
"timecode": "00:59:59:00",
"id": "0x1e0",
"r_frame_rate": "24000/1001",
"avg_frame_rate": "10000/417",
"time_base": "1/90000",
"start_time": "0.945411"
},
{
"index": 1,
"codec_name": "pcm_dvd",
"codec_long_name": "PCM signed 20|24-bit big-endian",
"codec_type": "audio",
"codec_time_base": "1/48000",
"codec_tag_string": "[0][0][0][0]",
"codec_tag": "0x0000",
"sample_fmt": "s32",
"sample_rate": "48000",
"channels": 2,
"bits_per_sample": 0,
"id": "0xa0",
"r_frame_rate": "0/0",
"avg_frame_rate": "0/0",
"time_base": "1/90000",
"start_time": "0.945411",
"duration": "600.595000"
}
],
"format": {
"filename": "/home/richard/projects/hello-python/tests/test_1.mpg",
"nb_streams": 2,
"format_name": "mpeg",
"format_long_name": "MPEG-PS format",
"start_time": "0.945411",
"duration": "600.595000",
"size": "4033241092",
"bit_rate": "53723272"
}
}
How can I access streams or format and then properties inside them? For example how to get codec_long_name from the second stream or how to get duration from format?
I tried:
print info[0]
Which outputs:
richard@richard-desktop:~/projects/hello-python$ python main.py
{
If I do print repr(info), I get:
richard@richard-desktop:~/projects/hello-python$ python main.py
'{\n "streams": [\n {\n "index": 0,\n "codec_name": "mpeg2video",\n "codec_long_name": "MPEG-2 video",\n "codec_type": "video",\n "codec_time_base": "1001/48000",\n "codec_tag_string": "[0][0][0][0]",\n "codec_tag": "0x0000",\n "width": 1920,\n "height": 1080,\n "has_b_frames": 1,\n "sample_aspect_ratio": "1:1",\n "display_aspect_ratio": "16:9",\n "pix_fmt": "yuv422p",\n "level": 2,\n "timecode": "00:59:59:00",\n "id": "0x1e0",\n "r_frame_rate": "24000/1001",\n "avg_frame_rate": "10000/417",\n "time_base": "1/90000",\n "start_time": "0.945411"\n },\n {\n "index": 1,\n "codec_name": "pcm_dvd",\n "codec_long_name": "PCM signed 20|24-bit big-endian",\n "codec_type": "audio",\n "codec_time_base": "1/48000",\n "codec_tag_string": "[0][0][0][0]",\n "codec_tag": "0x0000",\n "sample_fmt": "s32",\n "sample_rate": "48000",\n "channels": 2,\n "bits_per_sample": 0,\n "id": "0xa0",\n "r_frame_rate": "0/0",\n "avg_frame_rate": "0/0",\n "time_base": "1/90000",\n "start_time": "0.945411",\n "duration": "600.595000"\n }\n ],\n "format": {\n "filename": "/home/richard/projects/hello-python/tests/test_1.mpg",\n "nb_streams": 2,\n "format_name": "mpeg",\n "format_long_name": "MPEG-PS format",\n "start_time": "0.945411",\n "duration": "600.595000",\n "size": "4033241092",\n "bit_rate": "53723272"\n }\n}\n'
The way I am getting the JSON string is bu running this command:
ffmpeg_command = "ffprobe -v quiet -print_format json -show_format -show_streams %s" % self.absolute_path
return subprocess.check_output(ffmpeg_command, shell=True)
回答1:
The JSON was encoded twice, and the result of json.loads is a string. Strings in python are sequences thus the first character is a {.
Decode the item again:
info = json.loads(json.loads(get_info()))
Now your main.py output should look like:
>>> result = json.loads(output)
>>> print result
{u'streams': [{u'pix_fmt': u'yuv422p', u'index': 0, u'start_time': u'0.945411', u'codec_tag': u'0x0000', u'sample_aspect_ratio': u'1:1', u'level': 2, u'r_frame_rate': u'24000/1001', u'id': u'0x1e0', u'time_base': u'1/90000', u'codec_tag_string': u'[0][0][0][0]', u'codec_type': u'video', u'has_b_frames': 1, u'width': 1920, u'codec_long_name': u'MPEG-2 video', u'display_aspect_ratio': u'16:9', u'codec_name': u'mpeg2video', u'timecode': u'00:59:59:00', u'height': 1080, u'codec_time_base': u'1001/48000', u'avg_frame_rate': u'10000/417'}, {u'index': 1, u'sample_fmt': u's32', u'codec_tag': u'0x0000', u'bits_per_sample': 0, u'r_frame_rate': u'0/0', u'start_time': u'0.945411', u'time_base': u'1/90000', u'codec_tag_string': u'[0][0][0][0]', u'codec_type': u'audio', u'channels': 2, u'duration': u'600.595000', u'codec_long_name': u'PCM signed 20|24-bit big-endian', u'codec_name': u'pcm_dvd', u'id': u'0xa0', u'sample_rate': u'48000', u'codec_time_base': u'1/48000', u'avg_frame_rate': u'0/0'}], u'format': {u'nb_streams': 2, u'start_time': u'0.945411', u'format_long_name': u'MPEG-PS format', u'format_name': u'mpeg', u'filename': u'/home/richard/projects/hello-python/tests/test_1.mpg', u'bit_rate': u'53723272', u'duration': u'600.595000', u'size': u'4033241092'}}
and you can access the streams and format parameters by name:
>>> result['streams']
[{u'pix_fmt': u'yuv422p', u'index': 0, u'start_time': u'0.945411', u'codec_tag': u'0x0000', u'sample_aspect_ratio': u'1:1', u'level': 2, u'r_frame_rate': u'24000/1001', u'id': u'0x1e0', u'time_base': u'1/90000', u'codec_tag_string': u'[0][0][0][0]', u'codec_type': u'video', u'has_b_frames': 1, u'width': 1920, u'codec_long_name': u'MPEG-2 video', u'display_aspect_ratio': u'16:9', u'codec_name': u'mpeg2video', u'timecode': u'00:59:59:00', u'height': 1080, u'codec_time_base': u'1001/48000', u'avg_frame_rate': u'10000/417'}, {u'index': 1, u'sample_fmt': u's32', u'codec_tag': u'0x0000', u'bits_per_sample': 0, u'r_frame_rate': u'0/0', u'start_time': u'0.945411', u'time_base': u'1/90000', u'codec_tag_string': u'[0][0][0][0]', u'codec_type': u'audio', u'channels': 2, u'duration': u'600.595000', u'codec_long_name': u'PCM signed 20|24-bit big-endian', u'codec_name': u'pcm_dvd', u'id': u'0xa0', u'sample_rate': u'48000', u'codec_time_base': u'1/48000', u'avg_frame_rate': u'0/0'}]
Pro tip: use the pprint module to format python structures nicely:
>>> from pprint import pprint
>>> print pprint(result)
>>> pprint(result)
{u'format': {u'bit_rate': u'53723272',
u'duration': u'600.595000',
u'filename': u'/home/richard/projects/hello-python/tests/test_1.mpg',
u'format_long_name': u'MPEG-PS format',
u'format_name': u'mpeg',
u'nb_streams': 2,
u'size': u'4033241092',
u'start_time': u'0.945411'},
u'streams': [{u'avg_frame_rate': u'10000/417',
u'codec_long_name': u'MPEG-2 video',
u'codec_name': u'mpeg2video',
u'codec_tag': u'0x0000',
u'codec_tag_string': u'[0][0][0][0]',
u'codec_time_base': u'1001/48000',
u'codec_type': u'video',
u'display_aspect_ratio': u'16:9',
u'has_b_frames': 1,
u'height': 1080,
u'id': u'0x1e0',
u'index': 0,
u'level': 2,
u'pix_fmt': u'yuv422p',
u'r_frame_rate': u'24000/1001',
u'sample_aspect_ratio': u'1:1',
u'start_time': u'0.945411',
u'time_base': u'1/90000',
u'timecode': u'00:59:59:00',
u'width': 1920},
{u'avg_frame_rate': u'0/0',
u'bits_per_sample': 0,
u'channels': 2,
u'codec_long_name': u'PCM signed 20|24-bit big-endian',
u'codec_name': u'pcm_dvd',
u'codec_tag': u'0x0000',
u'codec_tag_string': u'[0][0][0][0]',
u'codec_time_base': u'1/48000',
u'codec_type': u'audio',
u'duration': u'600.595000',
u'id': u'0xa0',
u'index': 1,
u'r_frame_rate': u'0/0',
u'sample_fmt': u's32',
u'sample_rate': u'48000',
u'start_time': u'0.945411',
u'time_base': u'1/90000'}]}
回答2:
Try
from StringIO import StringIO
io = StringIO(get_info())
json.load(io)
回答3:
To print codec_long_name and duration from the second stream do the following:
details = subprocess.check_output(["C:/FFmpeg/bin/ffprobe.exe",
"-loglevel", "quiet", "-print_format", "json", "-show_streams",
file_path])
info = json.loads(details)
print info['streams'][1]['codec_long_name'], info['streams'][1]['duration']
来源：https://stackoverflow.com/questions/11241583/python-accessing-data-in-json-object