PRC: What are units of BinaryTextureData.texture_binary_data_size?

[ralovich]

Additional context
This is written against the PRC ISO standard 14739-1, First edition, dated 2014‐12‐15.

Describe the bug
What are units of BinaryTextureData.texture_binary_data_size? Is it number of bits or number of UnsignedIntegers?
Please consider adding a screenshot of the current version of BinaryTextureData in the working document.

[stuartgalt]

The current draft looks like:

My guess it is number of bits based on the texture_binary_data is an array of bits(8) and the size of the array is texture_binary_data_size/8

[socrat74]

texture_binary_data_size is the number of UnsignedIntegers (32-bit). The actual number of bits, if needed, can be found as texture_binary_data_size * 32 - last_integer_used_bit_number.
texuture_binary_data is an array of texture_binary_data_size * 32 bits.

[t3dr0]

Proposed Editorial Changes to PRC Specification (Revision 14 Nov 2025)

Subject: Defects in §7.8.9.9 (BinaryTextureData) and Table 177 — ambiguous units
of texture_binary_data_size and incorrect derived array size formula.

---

Change Request 1 — Clarify the description of texture_binary_data_size in Table 177

Location: §7.8.9.9, Table 177, description column for texture_binary_data_size

Before:

Name	Data Type	Data Description
texture_binary_data_size	UnsignedInteger	(Optional) texture_binary_data_size / 32

After:

Name	Data Type	Data Description
texture_binary_data_size	UnsignedInteger	(Optional) The number of 32-bit UnsignedIntegers in texture_binary_data. The total number of bits in texture_binary_data is therefore texture_binary_data_size * 32. The number of meaningful (non-padding) bits is texture_binary_data_size * 32 - last_integer_used_bit_number.

---

Change Request 2 — Correct the array size formula for texture_binary_data in Table 177

Location: §7.8.9.9, Table 177, Data Type and description columns for texture_binary_data

Before:

Name	Data Type	Data Description
texture_binary_data	Array <bits(8)>[texture_binary_data_size / 8]	(Optional) This size array is equal to texture_binary_data_size / 8.

After:

Name	Data Type	Data Description
texture_binary_data	Array <UnsignedInteger>[texture_binary_data_size]	(Optional) An array of texture_binary_data_size 32-bit UnsignedIntegers, each written as 4 bytes via MakePortable32BitsUnsigned (see §9.2). The total bit content is texture_binary_data_size * 32 bits, of which the last last_integer_used_bit_number bits are padding.

---

Change Request 3 — Correct the descriptive paragraph in §7.8.9.9

Location: §7.8.9.9, introductory paragraph

Before:

Then last_integer_used_bit_number bits are added to this array so that texture_binary_data_size
becomes a multiple of 32. Consequently, 0 ≤ last_integer_used_bit_number < 32. Then the unsigned
integer array is written byte by byte: each unsigned integer leads to 4 bytes obtained from
MakePortable32BitsUnsigned.

After:

The bit field is padded with last_integer_used_bit_number zero bits so that its total length becomes
a multiple of 32, where 0 ≤ last_integer_used_bit_number < 32. The padded bit field is then
partitioned into 32-bit words and stored as an array of UnsignedIntegers, the count of which is
recorded in texture_binary_data_size. Each unsigned integer is written as 4 bytes via
MakePortable32BitsUnsigned (see §9.2).

---

Change Request 4 — Give last_integer_used_bit_number a meaningful description in Table 177

Location: §7.8.9.9, Table 177, description column for last_integer_used_bit_number

Before:

Name	Data Type	Data Description
last_integer_used_bit_number	UnsignedInteger	(Optional) last_integer_used_bit_number

After:

Name	Data Type	Data Description
last_integer_used_bit_number	UnsignedInteger	(Optional) The number of padding bits appended to the bit field to bring its length to a multiple of 32. Satisfies 0 ≤ last_integer_used_bit_number < 32. The number of meaningful bits in texture_binary_data is texture_binary_data_size * 32 - last_integer_used_bit_number.