pespin has uploaded this change for review. (
https://gerrit.osmocom.org/c/libosmo-netif/+/30758 )
Change subject: amr: Clarify size of AMR BWE header and ToC
......................................................................
amr: Clarify size of AMR BWE header and ToC
Change-Id: I34c76b18ee45e12dba92864715e8ef91e6de3b01
---
M include/osmocom/netif/amr.h
M src/amr.c
2 files changed, 8 insertions(+), 4 deletions(-)
git pull ssh://gerrit.osmocom.org:29418/libosmo-netif refs/changes/58/30758/1
diff --git a/include/osmocom/netif/amr.h b/include/osmocom/netif/amr.h
index e8f08d4..9b8fb79 100644
--- a/include/osmocom/netif/amr.h
+++ b/include/osmocom/netif/amr.h
@@ -43,6 +43,9 @@
uint8_t data[0];
} __attribute__((packed));
+/* See diagram above: CMR (4) + F (1) + FT (4) + Q (1) = 10 */
+#define AMR_HDR_BWE_LEN_BITS 10
+
/*
* 4.4. Octet-aligned Mode:
*
diff --git a/src/amr.c b/src/amr.c
index e4f0dd8..18e699c 100644
--- a/src/amr.c
+++ b/src/amr.c
@@ -188,7 +188,7 @@
}
/* Calculate new payload length */
- bwe_payload_len = (10 + osmo_amr_bits(ft) + 7) / 8;
+ bwe_payload_len = (AMR_HDR_BWE_LEN_BITS + osmo_amr_bits(ft) + 7) / 8;
return bwe_payload_len;
}
@@ -266,7 +266,8 @@
amr_speech_len_bits = osmo_amr_bits(ft);
amr_speech_len_bytes = osmo_amr_bytes(ft);
- required_len_bits = amr_speech_len_bits + 10; /* shift of 10 bits */
+ /* shift of AMR_HDR_BWE_LEN_BITS (10) bits, aka remove BWE Hdr + ToC: */
+ required_len_bits = AMR_HDR_BWE_LEN_BITS + amr_speech_len_bits;
if (payload_len < (required_len_bits + 7)/8)
return -1;
@@ -288,7 +289,7 @@
int osmo_amr_iuup_to_bwe(uint8_t *payload, unsigned int payload_len,
unsigned int payload_maxlen)
{
- /* shift all bits by 10 */
+ /* shift all bits by AMR_HDR_BWE_LEN_BITS (10) */
unsigned int i, required_len_bits, required_len_bytes;
int ft = osmo_amr_bytes_to_ft(payload_len);
@@ -303,7 +304,7 @@
i = payload_len + 1;
payload[i] = (payload[i - 2] << 6);
for (i = payload_len; i >= 2; i--) {
- /* we have to shift the payload by 10 bits to get only the
Class A, B, C bits */
+ /* we have to shift the payload by AMR_HDR_BWE_LEN_BITS (10)
bits to prepend BWE Hdr + ToC */
payload[i] = (payload[i - 1] >> 2) | (payload[i - 2] << 6);
}
payload[i] = (payload[i - 1] >> 2);
--
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Gerrit-Project: libosmo-netif
Gerrit-Branch: master
Gerrit-Change-Id: I34c76b18ee45e12dba92864715e8ef91e6de3b01
Gerrit-Change-Number: 30758
Gerrit-PatchSet: 1
Gerrit-Owner: pespin <[email protected]>
Gerrit-MessageType: newchange
