The VideoLAN Forums

Posted: **11 Jan 2021 21:24**

I am trying to play and HEVC video with AAC-HE audio. The audio is a single track with 7 channels at 48KHz, but VLC identifies it as 24KHz in the log. Or am I interpreting this output wrong?

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[b1f74270] mpeg4audio packetizer: AAC channels: 7 samplerate: 24000

The playback sounds sort of crackly on the HDMI output which is easy to hear on this sample of 1KHz tone
https://mega.nz/file/U4QzVA5B#5jMCToBIi ... wWgmfaupww

I'm running on Raspbian Buster with the official build from apt repo (3.0.11-0-gdc0c5ced72). I've tried limiting the output to 2 channels but it still sounds crackly. I'm guessing that is because of the sample rate issue. I tried opening this file on a Windows PC with VLC 4.0 and it shows the same 24K sample rate in the message log. But the codec information window shows 48K and the audio playback sounds fine. I'm posting here in the general forum because the log output seems wrong on both machines.

Here is the MediaInfo:

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General
ID                                       : 0 (0x0)
Complete name                            : /Users/elliott/MEGAsync/Public/hevc-hd-8ch.ts
Format                                   : MPEG-TS
File size                                : 17.5 MiB
Duration                                 : 8 s 292 ms
Overall bit rate mode                    : Constant
Overall bit rate                         : 17.6 Mb/s

Video
ID                                       : 1001 (0x3E9)
Menu ID                                  : 1 (0x1)
Format                                   : HEVC
Format/Info                              : High Efficiency Video Coding
Format profile                           : Main 10@L5@High
Codec ID                                 : 36
Duration                                 : 8 s 333 ms
Width                                    : 1 920 pixels
Height                                   : 1 080 pixels
Display aspect ratio                     : 16:9
Frame rate                               : 24.000 FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 10 bits
Color range                              : Limited

Audio
ID                                       : 1002 (0x3EA)
Menu ID                                  : 1 (0x1)
Format                                   : AAC LC SBR
Format/Info                              : Advanced Audio Codec Low Complexity with Spectral Band Replication
Commercial name                          : HE-AAC
Format version                           : Version 4
Format settings                          : Implicit
Muxing mode                              : ADTS
Codec ID                                 : 15-2
Duration                                 : 8 s 277 ms
Bit rate mode                            : Variable
Channel(s)                               : 8 channels
Channel layout                           : C L R Ls Rs Lw Rw LFE
Sampling rate                            : 48.0 kHz
Frame rate                               : 23.438 FPS (2048 SPF)
Compression mode                         : Lossy
Delay relative to video                  : -28 ms

Posted: **12 Jan 2021 10:11**

I tried opening this file on a Windows PC with VLC 4.0 and it shows the same 24K sample rate in the message log. But the codec information window shows 48K and the audio playback sounds fine.

I haven't tried with VLC 4.x yet, but I can't reproduce the issue with VLC 3.0.11:

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main debug: using audio decoder module "faad"
faad debug: AAC SBR (channels: 8, samplerate: 48000)
directsound debug: Windows speaker config: Stereo and stream has 8 channels, using 2 channels
main debug: output 'f32l' 48000 Hz Stereo frame=1 samples/8 bytes
main debug: input 'f32l' 48000 Hz 3F2M2R/LFE frame=1 samples/32 bytes
scaletempo debug: format: 48000 rate, 8 nch, 4 bps, fl32

Posted: **13 Jan 2021 21:48**

I made a typo before, I meant to say this track has 8 channels.

I actually see those same lines too. I just didn't include the full verbose output before. Here it is: https://pastebin.com/raw/BzaimM7u
Here are some selected lines that seem relevant. Maybe the message about 7 channels and 24000Hz line is a red herring, but the real problem I'm trying to solve is that the audio sounds crackly.

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[b2f3eca0] main packetizer debug: using packetizer module "mpeg4audio"
[b2f3e678] main decoder debug: using audio decoder module "faad"
[b2f3eca0] mpeg4audio packetizer: AAC channels: 7 samplerate: 24000
[b2f3e678] main decoder debug: restarting module due to input format change
[b2f3e678] main decoder debug: removing module "faad"
[b2f3e678] main decoder debug: using audio decoder module "faad"
[b2f3e678] faad decoder debug: AAC SBR (channels: 8, samplerate: 48000)
[b288c8a0] main volume debug: using audio volume module "float_mixer"
[001e2150] main audio output debug: input 'f32l' 48000 Hz 3F2M2R/LFE frame=1 samples/32 bytes
[001e2150] main audio output debug: conversion: 'f32l'->'f32l' 48000 Hz->48000 Hz 3F2M2R/LFE->3F2M2R/LFE

Posted: **11 May 2022 05:22**

Seems VLC developers are not concerned about reporting correct bit rates in the media information codec dialog. When I play a VBR mp3 it always says 32kb/s. Also it says its a 32 bit file which is clearly wrong.
The dialog box says above it "Information about what your media or stream is made of"
Clearly incorrect information

Posted: **11 May 2022 13:30**

Seems VLC developers are not concerned about reporting correct bit rates in the media information codec dialog. When I play a VBR mp3 it always says 32kb/s. Also it says its a 32 bit file which is clearly wrong.
The dialog box says above it "Information about what your media or stream is made of"
Clearly incorrect information

https://forum.videolan.org/viewtopic.php?f=7&t=153646

Posted: **11 May 2022 14:08**

The packetiser disagrees with the decoder. Typically that would be caused by a bug in the software that muxed the file, but it's impossible to say without access to the file in question.

This may explain crackling, again impossible to confirm or infirm out of the blue.

Posted: **11 May 2022 17:11**

Seems VLC developers are not concerned about reporting correct bit rates in the media information codec dialog. When I play a VBR mp3 it always says 32kb/s. Also it says its a 32 bit file which is clearly wrong.
The dialog box says above it "Information about what your media or stream is made of"
Clearly incorrect information

https://forum.videolan.org/viewtopic.php?f=7&t=153646

i too have seen this minor issue but i can find out the bit depth properties of the audio file in question using another application rather than depending on the incorrect bit depth properties description from VLC.
i am happy that this issue is only affecting the audio properties bit depth description of VLC.
based on what i have read in the link to the discussion, it certainly does not appear any attention to this minor issue will be corrected, any time soon.
the attachment shows the audio properties description as 32Bits when in fact, the audio file is 16Bits.

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