def get_all_iter_mdf4(output, fmt):
x = MDF(r'test.mf4')
with Timer('Get all channels', f'asammdf {asammdf_version} mdfv4',
fmt) as timer:
for i, gp in enumerate(x.groups):
for j in range(len(gp['channels'])):
for k in x.iter_get(group=i, index=j, samples_only=True):
z = k
output.send([timer.output, timer.error])
