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[TobbeEdgeware]

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[alitteration]

Hello there,

I'm really not very familiar with go lang sadly, but I really appreciate the efforts you've put in that nice tool :)

I was wondering if you wouldn't mind helping me in what needs to be done to generate an EC-3 init for such information

StreamIndex Type="audio" QualityLevels="1" TimeScale="10000000" Language="eng" Name="audio_eng" Chunks="3224" Url="QualityLevels({bitrate})/Fragments(audio_eng={start time})">
<QualityLevel Index="0" Bitrate="192000" CodecPrivateData="00063F000000AF87FBA7022DFB42A4D405CD93843BDD0600200F00" FourCCData="0600200F00" SamplingRate="48000" Channels="6" BitsPerSample="16" PacketSize="768" AudioTag="65534" FourCC="EC-3"/

I saw in the test there is dec3Hex := "0000000e646563330c00200f0202"
but i don't know how to generate this from CodecPrivateData.

[tobbee]

Hi @alitteration,

Your snippet is from an MSS manifest. Unfortunately, I don't know what information is in the CodecPrivateData for EC-3 in MSS. Regarding the dec3Hex snippet in one of the example files of mp4ff, that is just a hex representation of a dec3 box as defined in https://github.com/edgeware/mp4ff/blob/master/mp4/dec3.go. If you have the information to fill in the structures for the Dec3Box you can generate such a box.

[tobbee]

A little more digging reveals that the CodecPrivateData should be a hex-encoded version of the the WAVE_FORMAT_EXTENSIBLE structure when the the AudioTab="65534". That format seems to be specified at https://learn.microsoft.com/en-us/windows/win32/api/mmeapi/ns-mmeapi-waveformatex. It doesn't help me to decipher the full string, though.

[thawancavalcante]

Hello there,
Can i use mp4ff to create different types of resolutions and fps?
I want to convert a .mp4 to HLS with multi-bitrate option.
Thanks

[tobbee]

mp4ff just does packaging/unpackaging of video, audio and subtitles, but does not change the actual encoded video or audio.

To change bitrate or resolution you need to use an encoder like x264/x265 directly or via ffmpeg etc.
Regarding HLS, mp4ff can generate segments in fMP4 format, but not the playlists needed.

[thawancavalcante]

Thank you for the explanation