Re: [FFmpeg-devel] [PATCH] avutil/frame: add av_frame_replace

[James Almer <jamrial@gmail.com>]

On 6/5/2022 12:42 PM, Andreas Rheinhardt wrote:
> James Almer:
>> Signed-off-by: James Almer <jamrial@gmail.com>
>> ---
>> Now taking into account the new channel layout API fields, supporting non
>> refcouted src, plus changing the documentation to state that the dst frame
>> properties will be replaced by those from src even if the data described
>> by both frames is the same.
>>
> 
> Apparently, you didn't get my point last time: What happens if dst and
> src coincide did not mean "what happpens if the data both frames refer
> to already coincides"; it meant "what happens if src == dst?" (so that
> there is only one AVFrame involved). You either disallow this altogether
> or you support it. This patch (and the last one) does neither.

Ok, will disallow this with

if (dst == src)
     return AVERROR(EINVAL);

How does av_frame_ref() handle this scenario, for that matter? The 
checks i see to ensure dst is clean (and thus one could assume is 
different than src) are non strict with av_assert1().

> 
>> Still missing APIChanges entry and version bump.
>>
>>   libavutil/frame.c | 144 ++++++++++++++++++++++++++++++++++++++++++++++
>>   libavutil/frame.h |  17 ++++++
>>   2 files changed, 161 insertions(+)
>>
>> diff --git a/libavutil/frame.c b/libavutil/frame.c
>> index 4c16488c66..2a4a2c27ad 100644
>> --- a/libavutil/frame.c
>> +++ b/libavutil/frame.c
>> @@ -461,6 +461,150 @@ fail:
>>       return ret;
>>   }
>>   
>> +int av_frame_replace(AVFrame *dst, const AVFrame *src)
>> +{
>> +    int i, ret = 0;
> 
> Why don't you use "for (int i = 0;" loop variables?

Because i copied this from av_frame_ref(). Will change it.

> 
>> +
>> +    dst->format         = src->format;
>> +    dst->width          = src->width;
>> +    dst->height         = src->height;
>> +    dst->nb_samples     = src->nb_samples;
>> +#if FF_API_OLD_CHANNEL_LAYOUT
>> +FF_DISABLE_DEPRECATION_WARNINGS
>> +    dst->channels       = src->channels;
>> +    dst->channel_layout = src->channel_layout;
>> +    if (!av_channel_layout_check(&src->ch_layout)) {
>> +        av_channel_layout_uninit(&dst->ch_layout);
>> +        if (src->channel_layout)
>> +            av_channel_layout_from_mask(&dst->ch_layout, src->channel_layout);
>> +        else {
>> +            dst->ch_layout.nb_channels = src->channels;
>> +            dst->ch_layout.order       = AV_CHANNEL_ORDER_UNSPEC;
>> +        }
>> +    } else {
>> +#endif
>> +    ret = av_channel_layout_copy(&dst->ch_layout, &src->ch_layout);
>> +    if (ret < 0)
>> +        goto fail;
>> +#if FF_API_OLD_CHANNEL_LAYOUT
>> +    }
>> +FF_ENABLE_DEPRECATION_WARNINGS
>> +#endif
>> +
>> +    wipe_side_data(dst);
>> +    av_dict_free(&dst->metadata);
>> +    ret = frame_copy_props(dst, src, 0);
>> +    if (ret < 0)
>> +        goto fail;
>> +
>> +    /* duplicate the frame data if it's not refcounted */
>> +    if (!src->buf[0]) {
>> +        for (i = 0; i < FF_ARRAY_ELEMS(dst->buf); i++)
>> +            av_buffer_unref(&dst->buf[i]);
>> +        for (i = 0; i < dst->nb_extended_buf; i++)
>> +            av_buffer_unref(&dst->extended_buf[i]);
>> +        av_freep(&dst->extended_buf);
>> +
>> +        memset(dst->data, 0, sizeof(dst->data));
>> +        if (dst->extended_data != dst->data)
>> +            av_freep(&dst->extended_data);
>> +
>> +        ret = av_frame_get_buffer(dst, 0);
>> +        if (ret < 0)
>> +            goto fail;
>> +
>> +        ret = av_frame_copy(dst, src);
>> +        if (ret < 0)
>> +            goto fail;
>> +
>> +        ret = av_buffer_replace(&dst->hw_frames_ctx, src->hw_frames_ctx);
>> +        if (ret < 0)
>> +            goto fail;
>> +
>> +        return 0;
>> +    }
>> +
>> +    /* replace the buffers */
>> +    for (i = 0; i < FF_ARRAY_ELEMS(src->buf); i++) {
>> +        ret = av_buffer_replace(&dst->buf[i], src->buf[i]);
>> +        if (ret < 0)
>> +            goto fail;
>> +    }
>> +
>> +    if (src->extended_buf) {
>> +        if (dst->nb_extended_buf != src->nb_extended_buf) {
>> +            int nb_extended_buf = FFMIN(dst->nb_extended_buf, src->nb_extended_buf);
>> +            void *tmp;
>> +
>> +            for (i = nb_extended_buf; i < dst->nb_extended_buf; i++)
>> +                av_buffer_unref(&dst->extended_buf[i]);
>> +
>> +            tmp = av_realloc_array(dst->extended_buf, sizeof(*dst->extended_buf),
>> +                                   src->nb_extended_buf);
>> +            if (!tmp) {
>> +                ret = AVERROR(ENOMEM);
>> +                goto fail;
>> +            }
>> +            dst->extended_buf = tmp;
>> +            dst->nb_extended_buf = src->nb_extended_buf;
>> +
>> +            memset(&dst->extended_buf[nb_extended_buf], 0,
>> +                   (src->nb_extended_buf - nb_extended_buf) * sizeof(*dst->extended_buf));
>> +        }
>> +
>> +        for (i = 0; i < src->nb_extended_buf; i++) {
>> +            ret = av_buffer_replace(&dst->extended_buf[i], src->extended_buf[i]);
>> +            if (ret < 0)
>> +                goto fail;
>> +        }
>> +    } else if (dst->extended_buf) {
>> +        for (i = 0; i < dst->nb_extended_buf; i++)
>> +            av_buffer_unref(&dst->extended_buf[i]);
>> +        av_freep(&dst->extended_buf);
>> +    }
>> +
>> +    ret = av_buffer_replace(&dst->hw_frames_ctx, src->hw_frames_ctx);
>> +    if (ret < 0)
>> +        goto fail;
>> +
>> +    if (dst->extended_data != dst->data)
>> +        av_freep(&dst->extended_data);
>> +
>> +    if (src->extended_data != src->data) {
>> +        int ch = src->ch_layout.nb_channels;
>> +
>> +#if FF_API_OLD_CHANNEL_LAYOUT
>> +FF_DISABLE_DEPRECATION_WARNINGS
>> +        if (!ch) {
>> +            ch = src->channels;
>> +            CHECK_CHANNELS_CONSISTENCY(src);
>> +        }
>> +FF_ENABLE_DEPRECATION_WARNINGS
>> +#endif
>> +        if (!ch) {
>> +            ret = AVERROR(EINVAL);
>> +            goto fail;
>> +        }
>> +
>> +        dst->extended_data = av_malloc_array(sizeof(*dst->extended_data), ch);
>> +        if (!dst->extended_data) {
>> +            ret = AVERROR(ENOMEM);
>> +            goto fail;
>> +        }
>> +        memcpy(dst->extended_data, src->extended_data, sizeof(*src->extended_data) * ch);
>> +    } else
>> +        dst->extended_data = dst->data;
>> +
>> +    memcpy(dst->data,     src->data,     sizeof(src->data));
>> +    memcpy(dst->linesize, src->linesize, sizeof(src->linesize));
>> +
>> +    return 0;
>> +
>> +fail:
>> +    av_frame_unref(dst);
>> +    return ret;
>> +}
>> +
>>   AVFrame *av_frame_clone(const AVFrame *src)
>>   {
>>       AVFrame *ret = av_frame_alloc();
>> diff --git a/libavutil/frame.h b/libavutil/frame.h
>> index 33fac2054c..a971b1655e 100644
>> --- a/libavutil/frame.h
>> +++ b/libavutil/frame.h
>> @@ -752,6 +752,23 @@ void av_frame_free(AVFrame **frame);
>>    */
>>   int av_frame_ref(AVFrame *dst, const AVFrame *src);
>>   
>> +/**
>> + * Ensure the destination frame refers to the same data described by the source
>> + * frame by creating a new reference for each AVBufferRef from src if they
>> + * differ from those in dst, or if src is not reference counted, by allocating
>> + * new buffers and copying data.
>> + *
>> + * Frame properties on dst will be replaced by those from src.
>> + *
>> + * @param src The source frame. If there's data described in it, it must be
>> + *            reference counted.
> 
> The text above says "if src is not reference counted, by allocating new
> buffers and copying data".

Remnant from the previous version. Will fix.

> 
>> + * @param dst The destination frame.
>> + *
>> + * @return 0 on success, a negative AVERROR on error. On error, dst is
>> + *         unreferenced.
>> + */
>> +int av_frame_replace(AVFrame *dst, const AVFrame *src);
>> +
>>   /**
>>    * Create a new frame that references the same data as src.
>>    *
> 
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