Media conversion in audb.load() does not load from cache

[hagenw]

When loading data the second time with audb.load() it will be much faster as the data is loaded from cache:

import audb

audb.config.SHARED_CACHE_ROOT ='./cache'
audb.config.CACHE_ROOT ='./cache'

table = 'emotion.categories.test.gold_standard'

db = audb.load('emodb', version='1.4.1', tables=table)  # ~90 s
db = audb.load('emodb', version='1.4.1', tables=table)  # ~ 1 s

It also works when requesting the same media format as the original one:

db = audb.load('emodb', version='1.4.1', tables=table, format='wav')  # ~90 s
db = audb.load('emodb', version='1.4.1', tables=table, format='wav')  # ~1 s

But this is no longer true when requesting a media format that is different from the original one (even though it is using the same cache folder in both calls):

db = audb.load('emodb', version='1.4.1', tables=table, format='flac')  # ~90 s
db = audb.load('emodb', version='1.4.1', tables=table, format='flac')  # ~90 s

[hagenw]

At the moment it fails to find the cached files as we are looking for missing files in audb.core.load._missing_files() with

audb/audb/core/load.py

Lines 876 to 877 in f8e992d

	if not os.path.exists(os.path.join(db_root, file)):
	missing_files.append(file)

But when we request format="flac", the cached file is file.flac and we are looking if file.wav exists.