[FFmpeg-devel,2/5] tests/api-flac-test: ensure the frame is writable before writing to it

The encoder may keep a reference to frames that were sent to it, so the
caller cannot modify them without checking first.
---
 tests/api/api-flac-test.c | 4 ++++
 1 file changed, 4 insertions(+)

On 2/24/2021 7:03 AM, Anton Khirnov wrote:
> The encoder may keep a reference to frames that were sent to it, so the
> caller cannot modify them without checking first.
> ---
>   tests/api/api-flac-test.c | 4 ++++
>   1 file changed, 4 insertions(+)
> 
> diff --git a/tests/api/api-flac-test.c b/tests/api/api-flac-test.c
> index 3fea3258f3..7c96a4d99e 100644
> --- a/tests/api/api-flac-test.c
> +++ b/tests/api/api-flac-test.c
> @@ -154,6 +154,10 @@ static int run_test(AVCodec *enc, AVCodec *dec, AVCodecContext *enc_ctx,
>           enc_pkt.data = NULL;
>           enc_pkt.size = 0;
>   
> +        result = av_frame_make_writable(in_frame);

This is going to make a copy of the existing frame data, only for the 
code below to completely replace it. It will also make copies (not 
references) of side data, if any.
Maybe instead unref it, set nb_samples, format and channel_layout again, 
then call av_frame_get_buffer() (Factoring the existing relevant code 
into its own function).

LGTM either way.

> +        if (result < 0)
> +            return result;
> +
>           generate_raw_frame((uint16_t*)(in_frame->data[0]), i, enc_ctx->sample_rate,
>                              enc_ctx->channels, enc_ctx->frame_size);
>           in_frame_bytes = in_frame->nb_samples * in_frame->channels * sizeof(uint16_t);
>

Quoting James Almer (2021-02-24 15:01:03)
> On 2/24/2021 7:03 AM, Anton Khirnov wrote:
> > The encoder may keep a reference to frames that were sent to it, so the
> > caller cannot modify them without checking first.
> > ---
> >   tests/api/api-flac-test.c | 4 ++++
> >   1 file changed, 4 insertions(+)
> > 
> > diff --git a/tests/api/api-flac-test.c b/tests/api/api-flac-test.c
> > index 3fea3258f3..7c96a4d99e 100644
> > --- a/tests/api/api-flac-test.c
> > +++ b/tests/api/api-flac-test.c
> > @@ -154,6 +154,10 @@ static int run_test(AVCodec *enc, AVCodec *dec, AVCodecContext *enc_ctx,
> >           enc_pkt.data = NULL;
> >           enc_pkt.size = 0;
> >   
> > +        result = av_frame_make_writable(in_frame);
> 
> This is going to make a copy of the existing frame data, only for the 
> code below to completely replace it. It will also make copies (not 
> references) of side data, if any.
> Maybe instead unref it, set nb_samples, format and channel_layout again, 
> then call av_frame_get_buffer() (Factoring the existing relevant code 
> into its own function).
> 
> LGTM either way.

Watches pelcome. I'd rather not spend more effort on this code than
strictly necessary.

On 3/1/2021 10:43 AM, Anton Khirnov wrote:
> Quoting James Almer (2021-02-24 15:01:03)
>> On 2/24/2021 7:03 AM, Anton Khirnov wrote:
>>> The encoder may keep a reference to frames that were sent to it, so the
>>> caller cannot modify them without checking first.
>>> ---
>>>    tests/api/api-flac-test.c | 4 ++++
>>>    1 file changed, 4 insertions(+)
>>>
>>> diff --git a/tests/api/api-flac-test.c b/tests/api/api-flac-test.c
>>> index 3fea3258f3..7c96a4d99e 100644
>>> --- a/tests/api/api-flac-test.c
>>> +++ b/tests/api/api-flac-test.c
>>> @@ -154,6 +154,10 @@ static int run_test(AVCodec *enc, AVCodec *dec, AVCodecContext *enc_ctx,
>>>            enc_pkt.data = NULL;
>>>            enc_pkt.size = 0;
>>>    
>>> +        result = av_frame_make_writable(in_frame);
>>
>> This is going to make a copy of the existing frame data, only for the
>> code below to completely replace it. It will also make copies (not
>> references) of side data, if any.
>> Maybe instead unref it, set nb_samples, format and channel_layout again,
>> then call av_frame_get_buffer() (Factoring the existing relevant code
>> into its own function).
>>
>> LGTM either way.
> 
> Watches pelcome. I'd rather not spend more effort on this code than
> strictly necessary.

Sure, apply this and i'll change it later.