ffprobe fails to get Monkey's Audio sample size

[ahthovaikied]

Take any Monkey's Audio file, it is reproducible with any MA file, but for the sake of example:

$ rsync rsync://fate-suite.libav.org/fate-suite/lossless-audio/luckynight-mac394b1-c2000.ape test.ape

Probe it:

$ ./ffprobe -show_format -show_streams test.ape 
ffprobe version N-73616-gfeb6a94 Copyright (c) 2007-2015 the FFmpeg developers
  built with gcc 4.8 (Ubuntu 4.8.4-2ubuntu1~14.04)
  configuration: --enable-gpl --enable-version3 --enable-nonfree --disable-runtime-cpudetect --disable-ffserver --disable-encoder=vorbis --disable-encoder=aac --enable-x11grab --enable-libfdk-aac --enable-libmp3lame --enable-libopus --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libxvid --disable-debug --cpu=corei7
  libavutil      54. 28.100 / 54. 28.100
  libavcodec     56. 47.100 / 56. 47.100
  libavformat    56. 40.100 / 56. 40.100
  libavdevice    56.  4.100 / 56.  4.100
  libavfilter     5. 21.100 /  5. 21.100
  libswscale      3.  1.101 /  3.  1.101
  libswresample   1.  2.100 /  1.  2.100
  libpostproc    53.  3.100 / 53.  3.100
Input #0, ape, from 'test.ape':
  Duration: 00:01:00.48, start: 0.000000, bitrate: 43 kb/s
    Stream #0:0: Audio: ape (APE  / 0x20455041), 44100 Hz, stereo, s16p
[STREAM]
index=0
codec_name=ape
codec_long_name=Monkey's Audio
profile=unknown
codec_type=audio
codec_time_base=1/44100
codec_tag_string=APE 
codec_tag=0x20455041
sample_fmt=s16p
sample_rate=44100
channels=2
channel_layout=stereo
bits_per_sample=0
id=N/A
r_frame_rate=0/0
avg_frame_rate=0/0
time_base=1/44100
start_pts=0
start_time=0.000000
duration_ts=2667168
duration=60.480000
bit_rate=N/A
max_bit_rate=N/A
bits_per_raw_sample=N/A
nb_frames=37
nb_read_frames=N/A
nb_read_packets=N/A
DISPOSITION:default=0
DISPOSITION:dub=0
DISPOSITION:original=0
DISPOSITION:comment=0
DISPOSITION:lyrics=0
DISPOSITION:karaoke=0
DISPOSITION:forced=0
DISPOSITION:hearing_impaired=0
DISPOSITION:visual_impaired=0
DISPOSITION:clean_effects=0
DISPOSITION:attached_pic=0
[/STREAM]
[FORMAT]
filename=test.ape
nb_streams=1
nb_programs=0
format_name=ape
format_long_name=Monkey's Audio
start_time=0.000000
duration=60.480000
size=328000
bit_rate=43386
probe_score=100
[/FORMAT]

Given this previous ticket ​https://trac.ffmpeg.org/ticket/3919#comment:5, I expected bits_per_raw_sample to be 16.

[Carl Eugen Hoyos]

Replying to ahthovaikied:

    Stream #0:0: Audio: ape (APE  / 0x20455041), 44100 Hz, stereo, s16p

bits_per_raw_sample is important for 24bit files because there is no other way to know they are 24bit. If the audio format is s16p, such a disambiguation should not be necessary.

[ahthovaikied]

From your comment in the other ticket I thought sample_fmt was only the internal sample representation used by FFmpeg, and that actual sample size could be anything below that.

If not, can you confirm that the right algorithm to reliably extract sample size is:

if value of 'bits_per_sample' > 0:
  return value of 'bits_per_sample'
else if value of 'bits_per_raw_sample' is set:
  return value of 'bits_per_raw_sample'
else extract sample size from 'sample_fmt' string

It looks complex for such simple task but I am looking for something reliable that works for every audio format on the surface of the earth.

Thanks

[Carl Eugen Hoyos]

Replying to ahthovaikied:

From your comment in the other ticket I thought sample_fmt was only the internal sample representation used by FFmpeg, and that actual sample size could be anything below that.

Below or equal, yes.

But I don't think anything with 8<bits_per_raw_sample<16 exists and since developers are lazy, they did not implement anything related yet.

[ahthovaikied]

Why not making bits_per_raw_sample always available if it is different from bits_per_sample?

[Carl Eugen Hoyos]

(It is always "available", I guess you mean "set".)
Patch welcome!

[Elon Musk]

Fixed in 505d6ed4756a68707c26e416646228d5ed31c0f5