Unable to play an M4A file #2055
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I'm trying to play files over FTP using a MultiDecoder. It works fine with MP3 and WAV: However M4A despite determining the type correctly I only get boinks and farts, and the decoder seems to be very confused: I have also found the ContainerMP4 class, but using that instead of the AAC Helix codec just gives me silence and the whole system appears frozen. Is there no solution to playing M4A files just yet? Thanks |
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Replies: 6 comments 23 replies
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M4A is a container format: I am not aware of any demuxer implementation that would run on a microcontroller... |
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Isn't the class I've linked at the end ( ) a barebones demuxer that exists in this very project?ESP-ADF has (somewhat limited) M4A support too, so in theory that is possible: https://github.com/espressif/esp-adf/blob/4200c64d4a78b9e9e2297818733aff21c72079a1/examples/cli/main/console_example.c#L387 (My Nokia phone from 2006 did M4A, and an ESP32 is way more powerful than that, so...) |
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Would you volunteer to test a new m4a demuxer and eventually a related alac decoder ? |
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Sure thing, I can do that, although I don't have any ALAC files remaining after migrating from iTunes when they destroyed it in 2017. But I have plenty of AAC/M4A ones! Is that the thing I've linked? If so, I got it to compile, but it didn't work for me, just freezes until the WDT kicks in. Fighting other issues in my own code in the mean time :-) |
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I committed some DRAFT ContainerM4A class: Just pass your MultiDecoder in the constructor and add an entry for "audio/m4a" which points to the ContainerM4A to the multidecoder. |
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Not sure if it's a good idea architecturally to do all the back and forth with switching MIMEs in the hot path of the decoding pipeline. I think it's better to just have a separate multidecoder for demuxing. One approach could be something like: graph TD
direction TB;
subgraph MultiDecoder
MP3'[MP3]
AAC'[AAC]
subgraph ContainerMP4
subgraph MultiDecoder'[MultiDecoder]
MP3
AAC
end
end
end
Since when the outer MultiDecoder selects the ContainerMP4 it will not be selecting MP3/AAC/etc, it's OK to pass the same objects into both by reference — no memory usage implications (at least for now). However a more logical approach if we then add more container formats would be something like this flowchart LR
style INPUT fill:#FFFFFF00, stroke:#FFFFFF00;
style OUTPUT fill:#FFFFFF00, stroke:#FFFFFF00;
INPUT[ ]-->MultiDemuxer
subgraph MultiDemuxer
direction TB;
ContainerMP4
ContainerMKV
ContainerOGG
ContainerNone
etc
end
MultiDemuxer-->MultiDecoder
subgraph MultiDecoder
direction TB;
DecoderAAC
DecoderMP3
DecoderWAV
end
MultiDecoder-->OUTPUT[ ]
(where ContainerNone is a fallback when detecting container type has failed, or demuxing is not necessary, e.g. MP3 file) This would also help with playing e.g. OGG files where you cannot know if it's Vorbis or OPUS until you demux it. |
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I agree that setting up a separate MultiDecoder would be a cleaner apprach since M4A can have only AAC and ALAC... |
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Just tried with latest master and after fixing a few typos it's still the same freeze with the strange size. It feels like it's missing some header unwrap before trying to go into the box decoding but I really need to dive into the code to find what exactly and I didn't have the time yet in the past days :( |
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I had a hard time to get the ALAC codec to work, but finaly it started to do what I expected. In order to be able to debug the m4a parsing, I added a test case that can be compiled and debugged on the desktop. |
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I'll try the latest version later tonight. Do you happen to have any guide about how to test it on desktop? As I have a few other things that are a bit confusing to debug and it seems that enabling I2S is breaking JTAG so I cannot debug on the device now... |
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In the example directory that I provided just execute the following This builds an executable that you can use with the debugger. |
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Tried the latest version, but it's crashing I guess due to (seems that the vector at fault is not created if that STSZ error is logged) If I set the box buffer size to be bigger than the default 8192 to a somewhat ridiculous 65536 bytes, then I can go past this error, so the box is being read correctly probably — but then there is an endless loop in the actual parsing right after that condition. |
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OK, the loop is not actually endless, it's just super long because of the use of a vector without resizing it in advance. Once it ends it goes further without a crash, albeit still no sound, and more weird boxes: |
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I was using generating the ContainerM4A implementation with AI. After digging into it I am not sure if I want to keep this! Can you share a m4a file ? |
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The email is sent, please take a look in case it might have gone to the spam folder |
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Hallo
Unfortunately the AAC is still not playing and I am hitting the problem, that I can't extract the AAC AudioSpecificConfig: The void onEsds(const MP4Parser::Box& box) is called as expected: but it seems that it does not conain any valid data. Any second opinion is wellcome.... |
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Is that with some specific file in the bunch or any file at all? Because there might be one or two files in there that survived multiple HDD head crashes so may be not exactly up to spec. I came down with a sudden fever but I'll take a look once I'm back up and running, thanks so much |
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Good news: I got the aac decoding working on the desktop. |
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More good news: m4a with alac is working now as well: so I have merged the code to main! Tomorrow I will do some tests on an ESP32... |
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M4A is a container format: I am not aware of any demuxer implementation that would run on a microcontroller...
You will need to convert thses files on the descktop to aac files e.g. using ffmpeg