DMR message decode issue #231

Saqibjaved25 · 2026-07-13T04:51:03Z

Saqibjaved25
Jul 13, 2026

I am running dsd-neo using dsd-neo.exe -i tcp:127.0.0.2:25500 then i transmit signal from DMR it give demode audio perfectly, but when i send a message from DMR, it get the signal but it doesn't give me decoded text. why?

Saqibjaved25 · 2026-07-13T11:18:04Z

Saqibjaved25
Jul 13, 2026
Author

Also i am facing [FLCO FEC ERR] due to which my audio data is being lost. how can i correct this error. i'm using DMR + RTL-SDR

16:16:07 Sync: +DMR MS/DM MODE/MONO | Color Code=01 | VC*
�[32m SLOT 1 TGT=16777215 SRC=31 Group Broadcast Call �[0m
16:16:07 Sync: +DMR MS/DM MODE/MONO | Color Code=01 | VC*
�[32m SLOT 1 TGT=16777215 SRC=31 Group Broadcast Call �[0m
16:16:07 Sync: +DMR MS/DM MODE/MONO | Color Code=01 | VC*
�[32m SLOT 1 TGT=16777215 SRC=31 Group Broadcast Call �[0m
16:16:08 Sync: +DMR MS/DM MODE/MONO | Color Code=01 | VC*
�[31m SLOT 1 FLCO FEC ERR �[0m�[31m (FEC ERR)�[0m
�[31m SLOT 1 SB/RC (FEC ERR) E:13; I:00B8E389 D:7FF; �[0m
16:16:09 Sync: +DMR MS/DM MODE/MONO | Color Code=00 | VC*
�[31m SLOT 1 FLCO FEC ERR �[0m�[31m (FEC ERR)�[0m
WARNING: Input Level LOW -40.8 dBFS: raise source/input volume if signal is present
16:16:10 Sync: +DMR MS/DM MODE/MONO | Color Code=04 | VC*
�[31m SLOT 1 FLCO FEC ERR �[0m�[31m (FEC ERR)�[0m
�[31m SLOT 1 SB/RC (FEC ERR) E:8; I:0389902E D:0D5; �[0m
16:16:10 Sync: +DMR MS/DM MODE/MONO | Color Code=03 | VC*
�[32m SLOT 1 TGT=16777215 SRC=31 Group Broadcast Call �[0m
16:16:11 Sync: +DMR MS/DM MODE/MONO | Color Code=01 | VC*

0 replies

arancormonk · 2026-07-14T20:58:16Z

arancormonk
Jul 14, 2026
Maintainer

Looking through this output, DSD-neo is detecting the DMR transmission and successfully reading the data header, but the actual message blocks are arriving corrupted.

The header says this is a confirmed Short Data message with nine 3/4-rate blocks and UTF-32 formatting. After that, nearly every R34C block reports:

(CRC ERR)

and the completed message ends with:

Multi Block PDU Message CRC32 ERR

Because the payload fails both the individual block checks and the final PDU CRC32 check, DSD-neo cannot safely display the text. Relaxing the CRC checks would not repair the message, it would most likely produce garbage.

The later output points to the same reception/input problem:

CACH/Burst FEC ERR
FLCO FEC ERR
Input Level LOW -40.8 dBFS

Voice can still sound acceptable while data messages fail because a multi-block data message needs every block to be received correctly.

A few things to check:

Confirm the TCP producer is sending signed PCM16LE, mono, at 48 kHz.
Raise the audio/source level in the SDR application; the incoming PCM level is currently low.
Make sure the signal is accurately centered and the SDR’s frequency correction is right.
Avoid an overly narrow NFM filter.
Disable noise reduction, audio EQ, or other processing that may distort the DMR discriminator audio.
Check RF gain and signal quality, but avoid turning the gain up far enough to overload the receiver.

--input-volume 2 can be tried as a quick test if the TCP audio itself is simply too quiet, but it will not improve RF SNR or repair distorted audio.

Could you also provide:

The exact DSD-neo version
Your complete command line
The SDR application and its NFM bandwidth/audio settings
A short, raw input recording covering one known test message

You can make the recording with something like:

dsd-neo.exe -fs -i tcp:127.0.0.2:25500 -6 dmr-test.wav

6 replies

Saqibjaved25 Jul 16, 2026
Author

Looking through this output, DSD-neo is detecting the DMR transmission and successfully reading the data header, but the actual message blocks are arriving corrupted.

The header says this is a confirmed Short Data message with nine 3/4-rate blocks and UTF-32 formatting. After that, nearly every R34C block reports:

(CRC ERR)

and the completed message ends with:

Multi Block PDU Message CRC32 ERR

Because the payload fails both the individual block checks and the final PDU CRC32 check, DSD-neo cannot safely display the text. Relaxing the CRC checks would not repair the message, it would most likely produce garbage.

The later output points to the same reception/input problem:

CACH/Burst FEC ERR FLCO FEC ERR Input Level LOW -40.8 dBFS

Voice can still sound acceptable while data messages fail because a multi-block data message needs every block to be received correctly.

A few things to check:

Confirm the TCP producer is sending signed PCM16LE, mono, at 48 kHz.

Raise the audio/source level in the SDR application; the incoming PCM level is currently low.

Make sure the signal is accurately centered and the SDR’s frequency correction is right.

Avoid an overly narrow NFM filter.

Disable noise reduction, audio EQ, or other processing that may distort the DMR discriminator audio.

Check RF gain and signal quality, but avoid turning the gain up far enough to overload the receiver.

--input-volume 2 can be tried as a quick test if the TCP audio itself is simply too quiet, but it will not improve RF SNR or repair distorted audio.

Could you also provide:

The exact DSD-neo version

Your complete command line

The SDR application and its NFM bandwidth/audio settings

A short, raw input recording covering one known test message

You can make the recording with something like:

dsd-neo.exe -fs -i tcp:127.0.0.2:25500 -6 dmr-test.wav
i am using dsd-neo VERSION 2.3.0,

Audio File: [dmr-test.wav](https://github.com/user-attachments/files/30073556/dmr-test.wav)

i send a message from DMR, "helo i am junior, its a text message".

arancormonk Jul 17, 2026
Maintainer

Thanks, the screenshots help. The 48 kHz mono TCP output and no de-emphasis look right. One thing that jumps out is the 50 kHz NFM bandwidth... that’s much too wide for a 12.5 kHz DMR channel. Try around 12.5–15 kHz and retest.

The new output is still showing CRC errors on every R34C block plus the final PDU CRC32 error, so DSD-neo still isn’t receiving an intact message payload.

There’s also a separate limitation here: the radio is sending Defined Short Data as format 0x16 (UTF-32), which v2.3.0 doesn’t currently decode properly. So even after the reception errors are fixed, this particular text format will need some decoder work.

I tried downloading dmr-test.wav, but the attachment is returning a 404. Could you upload it again, maybe as a ZIP? Your -6 dmr-test.wav command is correct. Once I can replay it, I should be able to tell how much is reception-related versus the UTF-32 limitation.

Saqibjaved25 Jul 17, 2026
Author

Thanks, the screenshots help. The 48 kHz mono TCP output and no de-emphasis look right. One thing that jumps out is the 50 kHz NFM bandwidth... that’s much too wide for a 12.5 kHz DMR channel. Try around 12.5–15 kHz and retest.

The new output is still showing CRC errors on every R34C block plus the final PDU CRC32 error, so DSD-neo still isn’t receiving an intact message payload.

There’s also a separate limitation here: the radio is sending Defined Short Data as format 0x16 (UTF-32), which v2.3.0 doesn’t currently decode properly. So even after the reception errors are fixed, this particular text format will need some decoder work.

I tried downloading dmr-test.wav, but the attachment is returning a 404. Could you upload it again, maybe as a ZIP? Your -6 dmr-test.wav command is correct. Once I can replay it, I should be able to tell how much is reception-related versus the UTF-32 limitation.

well! i tried on 12.5 and 15k but still facing same issue. let me show you the files.
https://drive.google.com/file/d/1xobzbfLW7TujZdp8Y8TE1oHa4-YPrrBc/view?usp=sharing

i've uploaded the .rar file here. with all the files and Readme.text please review them. and you've mentioned that v2.3.0 doesn’t currently decode properly format 0x16 (UTF-32), then is there any other version or way from which i can achieve my requirement?

arancormonk Jul 18, 2026
Maintainer

i implemented the decoder changes to support this, the latest nightly build has it: https://github.com/arancormonk/dsd-neo/releases/download/nightly/dsd-neo-msvc-x86_64-native-nightly.zip

Saqibjaved25 Jul 20, 2026
Author

Yes! Now i can see the text, currently i pulled the source code from your git, and i am trying to read it, i created .exe from that code, and using exe from release. please can you provide me the updated code or the file you've made changes, so that i can put it in the source folder? i am still learning many things and DSD is helping me alot.

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Saqibjaved25 Jul 13, 2026

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Saqibjaved25
Jul 13, 2026
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arancormonk
Jul 14, 2026
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Saqibjaved25 Jul 16, 2026
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Saqibjaved25 Jul 17, 2026
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arancormonk Jul 18, 2026
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Saqibjaved25 Jul 20, 2026
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