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11

This guide worked 100% for me - it takes you through each step. Afterwards, the m4a file plays! Note: this is completely free. http://sysfrontier.com/en/2014/12/31/hello-world/ Also pasting instructions in case the link goes down in future: How to fix corrupted voice memo (m4a) files. Do you have broken voice memo files? You can fix those files by ...


5

No. Once lossy formats are encoded, any data not saved within the file is lost. You could convert a lossy MP3 to a WAV or an M4A file but the quality of the WAV or M4A would be exactly the same as the original MP3.


3

You could try rewriting the file using ffmpeg with the following command: ffmpeg -i damagedfile.mp4 -c copy fixedfile.aac Alternatively you may use FAAD and a hex editor (e.g. Hexplorer). Find out where the actual data starts in a hex editor. Not always after the mdat entry - there may be alot of zeros in the beginning of the file. Simply copy everything ...


3

Raw PCM does not store stream properties, so when you ingest a raw PCM stream, ffmpeg assumes a sampling rate of 44100 Hz whereas your source is 48000 Hz. So new duration = old duration x (48000/44100). Export to WAV or AIFF using -c:a pcm_s16le. Alternatively, save as now and ingest using -f s16le -sample_rate 48000 -i temp.pcm. First method is recommended....


2

You can read up on how the Opus codec works here: http://opus-codec.org/ Opus is entirely open-source, so you can even read the source-code to determine how it works. Here is a paper on how MP3 and AAC work: https://www.iis.fraunhofer.de/content/dam/iis/de/doc/ame/conference/AES-17-Conference_mp3-and-AAC-explained_AES17.pdf These information sources ...


2

Yes, certain compression formats can result in higher peak levels than the same material pre-compression. -1dBTP ("true peak" level, relative to full scale) seems to be the accepted maximum safe level for pre-compressed material when considering this. It's important to ensure you are infact analysing true peak (aka. inter-sample peak) level and not sample ...


1

I've had this happen before, howevr it was while recording the screen of my computer. Not certain if you've done the same or used a camera IRL. However easiest way to see if there's audio in a file is to play the file in VLC and press CMD+I or CTRL+I (Window>Media Information) Notice under CODEC Details "Stream 0" & "Stream 1". 0 is your video and 1 is ...


1

Try opening the file with some advanced video players just to find out if the audio is gone or there's a codec error. Two video players that I use when having this sort of problems is Quick Time and Video Lan. If indeed there's no audio attached to the video - there's little to be done - maybe useing a disk data recovery tool depending on the recording ...


1

AAC-HE when having low bitrate considerations. MP3 if concerned about compatibility with all devices available. 112kbps mp3 could be a good compromise if you need both. More elaborate version: - AAC-HE requires your listener to have a special decoder installed and more computational power available, but uses a neat technology to "emulate" high frequency ...


1

How to fix corrupted voice memo (m4a) files – I have not tried it by myself but according to a bunch of comments it works.


1

As far as I know, m4a is also considered to be a lossy format. So converting from lossy to lossy would not make any difference, probably worsen the quality depending on the coding standard being used.


1

Just to add & clarify that m4a is a container format, actually the same spec as mp4, merely a different file extension, and therefore can contain either AAC (lossy) or ALAC (lossless) formats -- or even mp3! -- so the question as stated doesn't make sense (same with many of the answers & comments). Regardless, the simple answer to the intended ...


1

It is mathematically impossible to improve any digital audio stream to a "Better Quality" by a simple conversion to said file type. A poor quality mp3 can be "converted" to any format you like but the poor quality will remain and, as mentioned, you may even lose a bit in the conversion. There seems to be some misconceptions floating around out there about ...


1

It might be that you loose even more quality due to another file compression algorithm.


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