[MPD K20/21] Audio stopped working with CBCS encryption

[Trdum]

Bug report

Describe the bug

Recently my live television provider switched from CENC to CBCS encryption, unfortunately after this the audio playback stopped working.

Expected Behavior

Working video and audio when opening the live stream.

Actual Behavior

Stream opens without audio/sound and the video sometimes seems to be buffering every x seconds probably due to the audio not getting decrypted and decoded properly.

Kodi does show the audio tracks when you open the audio settings in the player, but there is no sound on both the audio tracks.

Possible Fix

See if there is a way to fix or add support for CBCS audio if this is the issue and not a codec problem.

To Reproduce

The live streams seem to be limited/locked to my ip or hostname by my isp, so you sadly won't be able to open them if your isp does not match.

Debuglog, DASH and MPD

You can find debug logs, dash files and mpd files here:
https://github.com/trdum/cbcsinput

Your Environment

Tested operating systems:

• Windows 11
• Android 13
• Linux Ubuntu 20.04
• macOS Big Sur

Tested Kodi versions:

• Kodi 18 and 19: No CBCS support so no video and audio.
• Kodi 20.5 / InputAdaptive 20.3.18: Video Ok, Audio None
• Kodi 21b3 / InputAdaptive 21.4.3: Video Ok, Audio None

[CastagnaIT]

with CBCS is shown these ffmpeg errors, imo this could be or bad decrypted data or not supported stream

2024-02-09 14:25:16.396 T:5728    debug <general>: ffmpeg[0x19f9ec37ce0]: [ac3] Multiple frames in a packet.
2024-02-09 14:25:16.396 T:5728    debug <general>: ffmpeg[0x19f9ec37ce0]: [ac3] Additional substreams is not implemented. Update your FFmpeg version to the newest one from Git. If the problem still occurs, it means that your file has a feature which has not been implemented.
2024-02-09 14:25:16.396 T:5728    debug <general>: ffmpeg[0x19f9ec37ce0]: [ac3] If you want to help, upload a sample of this file to https://streams.videolan.org/upload/ and contact the ffmpeg-devel mailing list. (ffmpeg-devel@ffmpeg.org)
2024-02-09 14:25:16.407 T:5728    error <general>: ffmpeg[0x19f9ec37ce0]: [ac3] invalid bitstream id
2024-02-09 14:25:16.407 T:5728    debug <general>: CVideoPlayerAudio: stream props changed, checking for passthrough
2024-02-09 14:25:16.407 T:5728     info <general>: CDVDAudioCodecFFmpeg::Open() Successful opened audio decoder ac3
2024-02-09 14:25:16.407 T:5728     info <general>: Creating audio stream (codec id: 86019, channels: 3, sample rate: 48000, no pass-through)

I can't help on that, maybe someone else will be able to provide help

[Trdum]

Thanks for taking the time to look into the issue.

I'm secretly hoping the ffmpeg/ac3 errors are caused because the audio isn't decrypted by inputstream adaptive making Kodi fail to playback the audio and output those errors in the logs because the audio stream it is trying to open is still encrypted and can't understand it this way.

When opening the CBCS streams in the web browser the audio works as it should, I did found a way to still access the CENC streams and the audio works in Kodi but most likely they will close those streams soon.

I tried to do some comparison between the CENC and CBCS audio streams using a few different tools but I can't detect much difference between the two, my knowledge analyzing and comparing streams is limited but here are some details:

So far I can see the streams provide two audio tracks one AC3 and one AAC.

CBCS and CENC both have the same audio tracks:
AC3 5chan (1633889587/86019) (ATSC A52 Dolby AC-3 Audio)
AAC 2chan (1836069985/86018) (AAC-LC ISO/IEC 13818-7 Audio with ADTS)

The audio tracks seem to be using identical codecs... as far as I can see, it also won't make much sense to me if they would use completely different audio codecs when the only logical difference should be the DRM to reduce unnecessary server load on their end.

Edit: added a few more dash examples to the logs that hopefully might help.

[glennguy]

All I can suggest is either
a) decryption isn't happening for audio or
b) decryption isn't happening correctly

The log is consistent with the audio decoder being fed junk... I'm inclined to think that it's just not being decrypted at all.

I don't think it's likely the files themselves are the wrong codec compared to what the manifest reports.

Are you able to provide more info on if/how we could reproduce this ourselves (is it a free service and is it geolocked)?
Alternatively if you can build inputstream.adaptive we could ask for a couple of log statements to insert into the decrypter to confirm whether audio decryption is happening or not.

[Trdum]

Thanks for the reply.

The live streams are provided by my ISP and seem to be locked to my ip or hostname, the requested mpd links expire after a few minutes so I unfortunately can't share the streams.

I can build inputstream adaptive manually and tried to change a few things but I don't have enough knowledge on how the CBCS decryption fully works, attaching visual studio debugger to Kodi doesn't work with DRM streams because Kodi crashes. (According to the wiki this is because of the encryption)

Just tried a few other free CBCS streams I found online, for example this one also only has working video and no audio on the CBCS stream:

Edit: converted to m3u playlists https://github.com/Trdum/cbcsplaylist

Stream URLs:
https://media.axprod.net/TestVectors/v9-MultiFormat/Clear/Manifest_1080p.mpd (VideoOk+AudioOk)
https://media.axprod.net/TestVectors/v9-MultiFormat/Encrypted_Cenc/Manifest_1080p.mpd (VideoOk+AudioOk)
https://media.axprod.net/TestVectors/v9-MultiFormat/Encrypted_Cbcs/Manifest_1080p.mpd (VideoOk+AudioFail)

License URL:
https://drm-widevine-licensing.axtest.net/AcquireLicense

Request header:
"X-AxDRM-Message": "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.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.k9OlwW0rUwuf5d5Eb0iO98AFR3qp7qKdFzSbg2PQj78"

Post data:
R{SSM}

Hope the audio not working on the stream above is caused by the same issue as my stream.

If this is not the case I can add extra debug logs to inputstream adaptive to help find the issue there.

Few more CBCS example streams I tested:
https://storage.googleapis.com/shaka-demo-assets/sintel-cbcs/dash.mpd (VideoOk+AudioOk)
https://github.com/Axinom/public-test-vectors/blob/master/axinom.exolist.json (VideoOk+AudioOk)
https://github.com/Axinom/public-test-vectors/blob/master/TestVectors-v9.md
https://refapp.hbbtv.org/production/catalogue/config.json

[glennguy]

Ok, you need to put something like this: LOG::Log(LOGDEBUG, "Decrypting sample - Stream Id: %u, mode: %u, crypt blocks: %u, skip blocks: %u", m_streamId, m_readerCryptoInfo.m_mode, m_readerCryptoInfo.m_cryptBlocks, m_readerCryptoInfo.m_skipBlocks); into FragmentedSampleReader.cpp:

Inbetween these 2 lines:

inputstream.adaptive/src/samplereader/FragmentedSampleReader.cpp

Lines 177 to 178 in 31dc91e

	m_sampleData.Reserve(m_encrypted.GetDataSize());
	if (AP4_FAILED(result =

and these 2 lines:

inputstream.adaptive/src/samplereader/FragmentedSampleReader.cpp

Lines 199 to 200 in 31dc91e

	m_sampleData.Reserve(m_encrypted.GetDataSize());
	m_singleSampleDecryptor->DecryptSampleData(m_poolId, m_encrypted, m_sampleData, nullptr, 0,

Mode should be 2 for CBCS and 1 for CENC (0 for unencrypted which shouldn't happen)
Crypt/Skip should be 1/9 for CBCS and 0/0 for CENC.

And of course for your CBCS stream you should be seeing log statements for both audio and video stream IDs e.g 1001, 1004... something like that.

I haven't actually compiled and tested myself but it should be right

[Trdum]

ISP Stream CBCS:

inputstream.adaptive: Decrypting sample 177178 - Stream Id: 1001, mode: 2, crypt blocks: 1, skip blocks: 9

Opening stream: 1001 source: 256 Creating video codec with codec id: 27
Opening stream: 1003 source: 256 Finding audio codec for: 86019

ISP Stream CENC:

inputstream.adaptive: Decrypting sample 177178 - Stream Id: 1001, mode: 1, crypt blocks: 0, skip blocks: 0
inputstream.adaptive: Decrypting sample 177178 - Stream Id: 1003, mode: 1, crypt blocks: 0, skip blocks: 0

Opening stream: 1001 source: 256 Creating video codec with codec id: 27
Opening stream: 1003 source: 256 Finding audio codec for: 86019

Test Axinom Stream CBCS:

AddOnLog: inputstream.adaptive: Decrypting sample 177178 - Stream Id: 1001, mode: 2, crypt blocks: 1, skip blocks: 9

Opening stream: 1001 source: 256 Creating video codec with codec id: 27
Opening stream: 1002 source: 256 Finding audio codec for: 86018

Test Axinom Stream CENC:

inputstream.adaptive: Decrypting sample 177178 - Stream Id: 1001, mode: 1, crypt blocks: 0, skip blocks: 0
inputstream.adaptive: Decrypting sample 177178 - Stream Id: 1002, mode: 1, crypt blocks: 0, skip blocks: 0

Opening stream: 1001 source: 256 Creating video codec with codec id: 27
Opening stream: 1002 source: 256 Finding audio codec for: 86018

Both my ISP and Axinom test CBCS stream seems to be skipping the audio track decryption.

On the CBCS streams I only see stream 1001 and it's not showing any logs for line 199/200, when I place the debug log on line 175 the audio track shows up as "Stream Id: 1002, mode: 0, crypt blocks: 0, skip blocks: 0"

Perhaps you can try to open the Axinom stream on your Kodi to see if you have the same result, guess this will also make it alot easier for you to find the issue using that stream, guessing the issue is the same as my ISP stream.

I made m3u files of the Axinom streams so you can easily open them as files in Kodi to test here:
https://github.com/Trdum/cbcsplaylist

Thanks for helping.

[glennguy]

Ok thanks for all that info, very helpful!

My usual Windows debugging trick of setting a sleep statement then attaching debugger and breaking afterwards isn't working atm, just crashes :/
I've traced the issue to here

inputstream.adaptive/src/samplereader/FragmentedSampleReader.cpp

Lines 378 to 379 in 31dc91e

	AP4_ContainerAtom* traf =
	AP4_DYNAMIC_CAST(AP4_ContainerAtom, moof->GetChild(AP4_ATOM_TYPE_TRAF, 0));

Even though the TRAF atom is there under the MOOF, it fails to get it

And from there the m_decrypter member is left empty and the next readsample will not try to decrypt.

So maybe a bug in bento4? @CastagnaIT have you had any luck recently with attaching debugger in Windows when widevine is involved?

Otherwise maybe we have to look at setting up some test code to load a file in and try that way...

[CastagnaIT]

unfurnately no way debugwith drm...
add some log the AP4_CencSampleInfoTable::Create return error -10 (AP4_ERROR_INVALID_FORMAT)

inputstream.adaptive/src/samplereader/FragmentedSampleReader.cpp

Lines 385 to 387 in 31dc91e

	if (AP4_FAILED(result = AP4_CencSampleInfoTable::Create(m_protectedDesc, traf, algorithm_id,
	reset_iv, *m_FragmentStream,
	moof_offset, sample_table)))

imo this happens on second part of Create method

https://github.com/xbmc/Bento4/blob/1f295b8a7c2c20c6398032dcfbf398ddb68a3300/Source/C%2B%2B/Core/Ap4CommonEncryption.cpp#L2788-L2789
or line
https://github.com/xbmc/Bento4/blob/1f295b8a7c2c20c6398032dcfbf398ddb68a3300/Source/C%2B%2B/Core/Ap4CommonEncryption.cpp#L2822-L2824

on video packet the saio/saiz/senc there are

but on audio packet these atoms seem to be all missing
i suspect that exit with last check for sample_info_table that return AP4_ERROR_INVALID_FORMAT

[CastagnaIT]

its similar situation about your old issue: axiomatic-systems/Bento4#781
but your old workaround is no more available on links maybe you remember something

[glennguy]

Yeah I can see that a workaround could be to create a senc atom.

I'm not having much luck. I can create a senc atom but can't get the sample count populated. Otherwise I can create the data for the atom but can't get it to dynamic cast. Or, we ask bento4 to help with this case upstream. What do you think?

[glennguy]

senc atom just needs to be 16 bytes and added as child to traf and set traf as parent

• UI32 for box size (00 00 00 16)
• UI32 for box type (AP4_ATOM_TYPE_SENC)
• UI32 for flags etc (00 00 00 00)
• UI32 for data - sample count eg. (00 00 00 BB) - trun->GetEntries().ItemCount()

[CastagnaIT]

i tested sample stream with shaka player that a/v works hoping to find some hint on sourcecode but without luck,
yeah it is worth trying to ask for some advice on how best to proceed to bento4 dev

[glennguy]

I've opened an issue at bento4 axiomatic-systems/Bento4#944