[FFmpeg-devel] Patch to libavc/opus to create extradata if missing

[Lynne]

Jan 3, 2021, 23:06 by jon at jonb.org:

> On Sun, Jan 3, 2021, at 12:50 PM, Andreas Rheinhardt wrote:
>
>>
>> It would be better if you used ff_alloc_extradata(): It also already
>> frees the extradata that might be present. And it does only set the
>> extradata_size after the allocation succeeded. But it is of course even
>> better if you actually errored out in case of allocation failure.
>>
>> Furthermore, your patch will lead to "declaration after statement" (or
>> something like that) warnings, because FFmpeg only allows variable
>> declarations at the beginning of each block (this is a remnant from C90).
>>
>
> Thanks Andreas!
>
> The patch now uses ff_alloc_extradata, and I moved the bitstream writer into its own function so it can create the bs variable on the stack.
>
> I wasn't sure of the best way to error out, since ff_rtp_parse_open doesn't return an error value. So I log the error and return NULL. Please advise if there is a better way.
>

> +    /* Input sample rate (0 = unspecified) */> +    bytestream_put_le32  (&bs, 0);
Put in 48000 here. Stream copy will preserve extradata, and we don't want to
generate weird streams, even if our decoder ignores this.

> +    /* Channel count */> +    bytestream_put_byte  (&bs, codecpar->channels);> +    /* Mapping family */> +    bytestream_put_byte  (&bs, 0x0);
This will only work for mono and stereo. The decoder will error out if more than
2 channels are present. For now maybe error out if the number of channels is greater than 2?