No audio with MP4 video files using mp4a at 48 kHz sample rate

[DAC324]

Hello all,

just today, I encountered a few MP4 video files that would not play with audio on VLC on Linux.

VLC version:

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VLC media player 3.0.10 Vetinari (revision 3.0.10-0-g7f145afa84) VLC-Version 3.0.10 Vetinari (3.0.10-0-g7f145afa84)

Linux distribution used:

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DISTRIB_ID=ManjaroLinux DISTRIB_RELEASE=20.0.3 DISTRIB_CODENAME=Lysia DISTRIB_DESCRIPTION="Manjaro Linux"

Codec information:

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Codec: MPEG AAC Audio (mp4a) Language: English Type: Audio Channels: 3F2R/LFE Sample Rate: 48000 Hz Bits per Sample: 32

Strange enough, there is not a lot of information found on the net. As I have a few videos where the audio sample rate is set to 44100 Hz (all other parameters the same as in the example), which all play flawlessly, I guessed the sample rate was the problem.

Instead, the solution is to change the preferred decoder to avcodec (see here and here).

Question is: What advantages does faad have over avcodec that it is used as the default in VLC?

Thank you very much for all insights in advance and kind regards,

DAC324

[DAC324]

Update:

This behavior also occurs with the latest VLC version 3.0.11 on Linux.
It looks like FAAD2 is not able to decode this kind of files as 48 kHz sample rate seems to be out of spec for this decoder.

InTheWings kindly advised me to have a look at the possibility of libfaad.so being replaced.

Unfortunately, the latest version of libfaad for Linux appears to be 2.0.0, and there seems to have been no update since 2017, according to the source available for download at the Audiocoding site.

Does anybody know if a newer libfaad version exists for Linux?

Thank you very much and kind regards,
DAC324

[Rémi Denis-Courmont]

VLC (on Windows or macOS) uses FAAD 2.9.2. This is also available on Debian...

[DAC324]

VLC (on Windows or macOS) uses FAAD 2.9.2. This is also available on Debian...

Thank you very much for this information.
Indeed, I must admit that I am a little bit confused:

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$ pacman -Qs faad2 local/faad2 2.9.2-1 ISO AAC audio decoder

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$ ls -l /usr/lib/libfaad* lrwxrwxrwx 1 root root 20 5. Mai 11:58 /usr/lib/libfaad_drm.so -> libfaad_drm.so.2.0.0 lrwxrwxrwx 1 root root 20 5. Mai 11:58 /usr/lib/libfaad_drm.so.2 -> libfaad_drm.so.2.0.0 -rwxr-xr-x 1 root root 251800 5. Mai 11:58 /usr/lib/libfaad_drm.so.2.0.0 lrwxrwxrwx 1 root root 16 5. Mai 11:58 /usr/lib/libfaad.so -> libfaad.so.2.0.0 lrwxrwxrwx 1 root root 16 5. Mai 11:58 /usr/lib/libfaad.so.2 -> libfaad.so.2.0.0 -rwxr-xr-x 1 root root 264088 5. Mai 11:58 /usr/lib/libfaad.so.2.0.0

Looks like the package version available here is indeed 2.9.2-1 but it installs libfaad*.2.0.0

Also, I had a look in the FAAD2 source. In decoder.c, it says:

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hDecoder->config.defSampleRate = 44100; /* Default: 44.1kHz */

But on the other hand, 48 kHz appears to be a valid sample rate, anyway (common.c):

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/* Returns the sample rate based on the sample rate index */ uint32_t get_sample_rate(const uint8_t sr_index) { static const uint32_t sample_rates[] = { 96000, 88200, 64000, 48000, 44100, 32000, 24000, 22050, 16000, 12000, 11025, 8000 };

Looks like there is a bug in FAAD2 (at least on Linux) preventing it to handle the 48 kHz sample rate properly.

Kind regards,
DAC324

[InTheWings]

Looks like the package version available here is indeed 2.9.2-1 but it installs libfaad*.2.0.0

2.0.0 is the API/ABI numbering, not library version

[DAC324]

Hello,

just to provide some update. Meanwhile, faad2 has been updated to package version 2.10.0-1 but the problem with the sample rate of 48 kHz not being processed properly, still persists.

Kind regards,
DAC324

[InTheWings]

Hello,

just to provide some update. Meanwhile, faad2 has been updated to package version 2.10.0-1 but the problem with the sample rate of 48 kHz not being processed properly, still persists.

Kind regards,
DAC324

Provide a way to reproduce the issue

[DAC324]

Provide a way to reproduce the issue

At first, you need a video file with the following specifications:

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Stream 0 Codec: H264 - MPEG-4 AVC (part10) (avc1) Type: Video Video Resolution: 1280 x 720 Buffer Size: 1280 x 720 Frame Rate: 23.976032 Decoded Format: <empty> Alignment: Upper left Basic Colors: ITU-R BT.709 Color transmission function: ITU-R BT.709 Color Space: ITU-R BT.709 area Color saturation shift: Left Stream 1 Codec: MPEG AAC Audio (mp4a) Language: English Type: Audio Channels: Stereo Sample Rate: 48000 Hz Bits per Sample: 32

When such a video file is started, I only get video but no audio.
What you will have to do is:

In Tools > Settings (all) > Input/Codecs > Videocodecs > List of preferred decoders, you will have to enter

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avcodec

and save. With that setting, the video in question plays fine, including audio. As soon as this avcodec entry is omitted, there is again silence instead of the audio.

Interesting: As soon as avcodec is enabled, the codec information changes from

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Channels: Stereo

to

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Channels: 3F2R/LFE

Looks like the default faad decoder is not able to determine the channel configuration and hence, just does not play any audio at all.

[DAC324]

As I cannot update my previous posting, I add this information here:

Without avcodec included in the list of preferred decoders, Video playback also stutters and has color artifacts (vlc 4.0.0).

[InTheWings]

no file no test no fix

[DAC324]

no file no test no fix

Problem is that the video file in question is copyright protected. I did a search for a free sample video file with the same specifications (as shown in VLC) but there, the error did not occur. Is there a way to get more comprehensive audio/video format information than the one shown in VLC's codec information window?
I started vlc from terminal with this video and get:

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VLC media player 4.0.0-dev Otto Chriek (revision 03674ae) [h264 @ 0x7fb41deb2b40] nal_unit_type: 7(SPS), nal_ref_idc: 3 [h264 @ 0x7fb41deb2b40] nal_unit_type: 8(PPS), nal_ref_idc: 3 [h264 @ 0x7fb41deb2b40] nal_unit_type: 5(IDR), nal_ref_idc: 3 [swscaler @ 0x7fb4140e7440] Forcing full internal H chroma due to input having non subsampled chroma [h264 @ 0x7fb41deb2b40] Format yuv420p chosen by get_format(). [h264 @ 0x7fb41deb2b40] Reinit context to 1280x720, pix_fmt: yuv420p [h264 @ 0x7fb41deb2b40] no picture [h264 @ 0x7fb41defb900] nal_unit_type: 1(Coded slice of a non-IDR picture), nal_ref_idc: 2 [h264 @ 0x7fb41defb900] no picture [h264 @ 0x7fb41df18600] nal_unit_type: 1(Coded slice of a non-IDR picture), nal_ref_idc: 2

Log file is here.

With avcodec set in the list of preferred decoders, I get the following (similar) output in the terminal:

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LC media player 4.0.0-dev Otto Chriek (revision 03674ae) [h264 @ 0x7f3879eb2b40] nal_unit_type: 7(SPS), nal_ref_idc: 3 [h264 @ 0x7f3879eb2b40] nal_unit_type: 8(PPS), nal_ref_idc: 3 [h264 @ 0x7f3879eb2b40] nal_unit_type: 5(IDR), nal_ref_idc: 3 [swscaler @ 0x7f38700e5a00] Forcing full internal H chroma due to input having non subsampled chroma [h264 @ 0x7f3879eb2b40] Format yuv420p chosen by get_format(). [h264 @ 0x7f3879eb2b40] Reinit context to 1280x720, pix_fmt: yuv420p [h264 @ 0x7f3879eb2b40] no picture [h264 @ 0x7f3879efb900] nal_unit_type: 1(Coded slice of a non-IDR picture), nal_ref_idc: 2 [h264 @ 0x7f3879efb900] no picture [h264 @ 0x7f3879f18600] nal_unit_type: 1(Coded slice of a non-IDR picture), nal_ref_idc: 2 [h264 @ 0x7f3879f35300] nal_unit_type: 1(Coded slice of a non-IDR picture), nal_ref_idc: 0 [h264 @ 0x7f3879f52000] nal_unit_type: 1(Coded slice of a non-IDR picture), nal_ref_idc: 0 [h264 @ 0x7f3879eb2b40] nal_unit_type: 1(Coded slice of a non-IDR picture), nal_ref_idc: 2 [h264 @ 0x7f3879efb900] nal_unit_type: 1(Coded slice of a non-IDR picture), nal_ref_idc: 2

Log File is here.

Apparently, without avcodec, the main difference is here:

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pulse debug: started pulse debug: changing sink 0: alsa_output.pci-0000_00_1b.0.analog-stereo (Internes Audio Analog Stereo) qt warning: qml error qrc:/widgets/DragItem.qml:52 ReferenceError: g_mainDisplay is not defined ... qt debug: on_player_track_list_changed (audio) pulse error: overflow, flushing vlcpulse debug: write index corrupt

Consequently, I get

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main warning: picture is too late to be displayed (missing 4391 ms) main warning: picture is too late to be displayed (missing 4336 ms) main warning: picture is too late to be displayed (missing 4280 ms) main warning: picture is too late to be displayed (missing 4224 ms) main warning: picture is too late to be displayed (missing 4169 ms) ...

The same section with avcodec looks better:

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pulse debug: changing sink 0: alsa_output.pci-0000_00_1b.0.analog-stereo (Internes Audio Analog Stereo) pulse debug: started ... qt debug: on_player_track_list_changed (audio) main debug: looking for extension module matching "any": 1 candidates

- and there are no "picture is too late" errors.

[InTheWings]

no file no test no fix

Problem is that the video file in question is copyright protected. I did a search for a free sample video file with the same specifications (as shown in VLC) but there, the error did not occur. Is there a way to get more comprehensive audio/video format information than the one shown in VLC's codec information window?

If you can't see the problem with other files, we also can't.

[DAC324]

If you can't see the problem with other files, we also can't.

Here is what mediainfo says about this file:

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General Complete name : vlc_test.720p.mp4 Format : MPEG-4 Format profile : Base Media Codec ID : isom (isom/iso2/avc1/mp41) File size : 984 MiB Duration : 30 min 2 s Overall bit rate mode : Variable Overall bit rate : 4 579 kb/s Writing application : Lavf58.20.100 Video ID : 1 Format : AVC Format/Info : Advanced Video Codec Format profile : High@L3.1 Format settings : CABAC / 4 Ref Frames Format settings, CABAC : Yes Format settings, Reference frames : 4 frames Codec ID : avc1 Codec ID/Info : Advanced Video Coding Duration : 30 min 2 s Bit rate mode : Constant Bit rate : 3 933 kb/s Nominal bit rate : 6 000 kb/s Width : 1 280 pixels Height : 720 pixels Display aspect ratio : 16:9 Frame rate mode : Variable Frame rate : 23.976 (24000/1001) FPS Minimum frame rate : 23.810 FPS Maximum frame rate : 24.390 FPS Color space : YUV Chroma subsampling : 4:2:0 Bit depth : 8 bits Scan type : Progressive Bits/(Pixel*Frame) : 0.178 Stream size : 845 MiB (86%) Color range : Limited Color primaries : BT.709 Transfer characteristics : BT.709 Matrix coefficients : BT.709 Codec configuration box : avcC Audio ID : 2 Format : AAC LC Format/Info : Advanced Audio Codec Low Complexity Codec ID : mp4a-40-2 Duration : 30 min 2 s Duration_LastFrame : -5 ms Bit rate mode : Constant Bit rate : 639 kb/s Channel(s) : 6 channels Channel layout : L R C Cb Lb Rb Sampling rate : 48.0 kHz Frame rate : 46.875 FPS (1024 SPF) Compression mode : Lossy Stream size : 137 MiB (14%) Language : English Default : Yes Alternate group : 1 Text ID : 3 Format : Timed Text Muxing mode : sbtl Codec ID : tx3g Duration : 29 min 54 s Bit rate mode : Variable Bit rate : 93 b/s Stream size : 20.3 KiB (0%) Title : English (CC) Language : English Default : Yes Forced : No Alternate group : 3

[Rémi Denis-Courmont]

No sample, no bug. We can't do magic.

[DAC324]

No sample, no bug. We can't do magic.

I understand. But I do not want to post a link to this file publicly here in the forum. Is there another way to send the sample to you?

[InTheWings]

http://streams.videolan.org/upload/

[DAC324]

http://streams.videolan.org/upload/

File uploaded. Thanks a bunch for providing this opportunity.