To generate this patch, we can follow these reasoning steps:

Step 1. Root Cause Analysis:

1. Identify the vulnerable operation:
   - The vulnerability is in the call to `av_new_packet()`, where the size argument is calculated as `8 + (32 + 4 + size) * codec->channels`.

2. Analyze potential issues:
   - Integer overflow can occur if `size` or `codec->channels` are large enough.
   - The result of the multiplication could exceed INT_MAX, leading to a negative or unexpectedly small allocation.

3. Determine the risk:
   - If an integer overflow occurs, it could lead to a buffer that's smaller than intended.
   - This could result in out-of-bounds writes (CWE-787) when the buffer is used.

Step 2. Fixing Strategy:

1. Prevent integer overflow:
   - Check if `size` is too large: `size > (INT_MAX - 32 - 4)`
   - Check if `(32 + 4 + size)` multiplied by `codec->channels` would overflow: `(32 + 4 + size) > (INT_MAX / codec->channels)`
   - Check if the final addition of 8 would overflow: `(32 + 4 + size) * codec->channels > INT_MAX - 8`

2. Handle error cases:
   - If any of these checks fail, return an error code (AVERROR_INVALIDDATA).

3. Maintain existing functionality:
   - Keep the original `av_new_packet()` call if all checks pass.

4. Implement the fix:
   - Add the overflow checks before the `av_new_packet()` call.
   - Return an error if any check fails.

The resulting patch implements these checks, preventing integer overflow and potential buffer overflow, thus addressing the CWE-787 vulnerability.