[FFmpeg-user] Strange output of ffprobe

[Анатолий Коростелев]

Hello!

Recently I recieved a mp4 for playing. When I tried to play this file I 
didn't hear any sound in some players (in ffplay sound worked). When I 
looked at the metadata of this file (via ffprobe), I saw the following:

$ ffprobe 6kad_16_144p.mp4
ffprobe version 3.1.4 Copyright (c) 2007-2016 the FFmpeg developers
   built with Apple LLVM version 8.0.0 (clang-800.0.38)
   configuration: --prefix=/usr/local/Cellar/ffmpeg/3.1.4 
--enable-shared --enable-pthreads --enable-gpl --enable-version3 
--enable-hardcoded-tables --enable-avresample --cc=clang --host-cflags= 
--host-ldflags= --enable-opencl --enable-libx264 --enable-libmp3lame 
--enable-libxvid --enable-libfreetype --enable-libvorbis --enable-libvpx 
--enable-libass --enable-libfdk-aac --enable-libopus --enable-libx265 
--disable-lzma --enable-nonfree --enable-vda
   libavutil      55. 28.100 / 55. 28.100
   libavcodec     57. 48.101 / 57. 48.101
   libavformat    57. 41.100 / 57. 41.100
   libavdevice    57.  0.101 / 57.  0.101
   libavfilter     6. 47.100 /  6. 47.100
   libavresample   3.  0.  0 /  3.  0.  0
   libswscale      4.  1.100 /  4.  1.100
   libswresample   2.  1.100 /  2.  1.100
   libpostproc    54.  0.100 / 54.  0.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '6kad_16_144p.mp4':
   Metadata:
     major_brand     : isom
     minor_version   : 512
     compatible_brands: isomiso2avc1mp41
     creation_time   : 2016-10-04 13:33:08
     encoder         : Lavf57.51.100
   Duration: 00:22:49.90, start: 0.000000, bitrate: 335 kb/s
     Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p, 
256x144 [SAR 1:1 DAR 16:9], 201 kb/s, 25 fps, 25 tbr, 12800 tbn, 50 tbc 
(default)
     Metadata:
       creation_time   : 2016-10-04 13:33:08
       handler_name    : VideoHandler
     Stream #0:1(und): Audio: aac (mp4a / 0x6134706D), 48000 Hz, stereo, 
fltp, 128 kb/s (default)
     Metadata:
       creation_time   : 2016-10-04 13:33:08
       handler_name    : SoundHandler


Then I used mediainfo utility to see the metadata of the file:

$ mediainfo 6kad_16_144p.mp4
General
Complete name                            : 6kad_16_144p.mp4
Format                                   : MPEG-4
Format profile                           : Base Media
Codec ID                                 : isom (isom/iso2/avc1/mp41)
File size                                : 54.8 MiB
Duration                                 : 22 min 49 s
Overall bit rate                         : 336 kb/s
Encoded date                             : UTC 2016-10-04 13:33:08
Tagged date                              : UTC 2016-10-04 13:33:08
Writing application                      : Lavf57.51.100

Video
ID                                       : 1
Format                                   : AVC
Format/Info                              : Advanced Video Codec
Format profile                           : Main at L4.1
Format settings, CABAC                   : Yes
Format settings, ReFrames                : 2 frames
Codec ID                                 : avc1
Codec ID/Info                            : Advanced Video Coding
Duration                                 : 22 min 49 s
Bit rate                                 : 200 kb/s
Width                                    : 256 pixels
Height                                   : 144 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Constant
Frame rate                               : 25.000 FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Progressive
Bits/(Pixel*Frame)                       : 0.217
Stream size                              : 32.9 MiB (60%)
Writing library                          : x264 core 148 r2721
Encoding settings                        : cabac=1 / ref=2 / 
deblock=1:0:0 / analyse=0x1:0x131 / me=hex / subme=7 / psy=1 / 
psy_rd=1.00:0.00 / mixed_ref=0 / me_range=16 / chroma_me=1 / trellis=1 / 
8x8dct=0 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=-2 / 
threads=3 / lookahead_threads=1 / sliced_threads=0 / nr=0 / decimate=1 / 
interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=3 / 
b_pyramid=0 / b_adapt=1 / b_bias=0 / direct=0 / weightb=1 / open_gop=0 / 
weightp=2 / keyint=250 / keyint_min=25 / scenecut=40 / intra_refresh=0 / 
rc_lookahead=40 / rc=abr / mbtree=1 / bitrate=200 / ratetol=1.0 / 
qcomp=0.60 / qpmin=10 / qpmax=69 / qpstep=4 / vbv_maxrate=8500 / 
vbv_bufsize=24000 / nal_hrd=none / filler=0 / ip_ratio=1.40 / aq=3:1.00
Encoded date                             : UTC 2016-10-04 13:33:08
Tagged date                              : UTC 2016-10-04 13:33:08

Audio
ID                                       : 2
Format                                   : ER Parametric
Format/Info                              : Advanced Audio Codec
Codec ID                                 : 40
Duration                                 : 22 min 49 s
Bit rate mode                            : Constant
Bit rate                                 : 128 kb/s
Channel(s)                               : 2 channels
Sampling rate                            : 7 350 Hz
Frame rate                               : 7.178 FPS (1024 spf)
Compression mode                         : Lossy
Stream size                              : 21.0 MiB (38%)
Default                                  : Yes
Alternate group                          : 1
Encoded date                             : UTC 2016-10-04 13:33:08
Tagged date                              : UTC 2016-10-04 13:33:08


As you can see the "Sampling rate" in mediainfo is 7 350 Hz (it's 
illegal value) while "Sampling rate" in ffprobe is 48000 Hz. I think 
that the problem with the sound of this file has been caused by encoder 
errors/misconfiguration. But it's very strange that ffrobe always shows 
me 48000 Hz Sampling rate. Is this a bug or something else?

P.S. This mp4 file is available here https://yadi.sk/i/Ew77H8kiwpG7r


--
Sincerely,
Anatoliy V. Korostelev