On 3/21/2018 2:14 PM, James Almer wrote:
> On 3/19/2018 1:49 PM, James Almer wrote:
>> On 3/19/2018 1:32 PM, wm4 wrote:
>>> On Mon, 19 Mar 2018 12:42:16 -0300
>>> James Almer <jamr...@gmail.com> wrote:
>>>
>>>> Useful as well to quickly make a packet reference counted when it
>>>> isn't already so.
>>>>
>>>> Signed-off-by: James Almer <jamr...@gmail.com>
>>>> ---
>>>> libavcodec/avcodec.h | 11 +++++++++++
>>>> libavcodec/avpacket.c | 24 ++++++++++++++++++++++++
>>>> 2 files changed, 35 insertions(+)
>>>>
>>>> diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h
>>>> index a8322fb62a..a78017f1fb 100644
>>>> --- a/libavcodec/avcodec.h
>>>> +++ b/libavcodec/avcodec.h
>>>> @@ -4518,6 +4518,17 @@ void av_packet_move_ref(AVPacket *dst, AVPacket
>>>> *src);
>>>> */
>>>> int av_packet_copy_props(AVPacket *dst, const AVPacket *src);
>>>>
>>>> +/**
>>>> + * Create a writable reference for the data described by a given packet,
>>>> + * avoiding data copy if possible.
>>>> + *
>>>> + * @param pkt Packet whose data should be made writable.
>>>> + *
>>>> + * @return 0 on success, a negative AVERROR on failure. On failure, the
>>>> + * packet is unchanged.
>>>> + */
>>>> +int av_packet_make_writable(AVPacket *pkt);
>>>> +
>>>> /**
>>>> * Convert valid timing fields (timestamps / durations) in a packet from
>>>> one
>>>> * timebase to another. Timestamps with unknown values (AV_NOPTS_VALUE)
>>>> will be
>>>> diff --git a/libavcodec/avpacket.c b/libavcodec/avpacket.c
>>>> index fe8113ab76..0693ca6f62 100644
>>>> --- a/libavcodec/avpacket.c
>>>> +++ b/libavcodec/avpacket.c
>>>> @@ -652,6 +652,30 @@ void av_packet_move_ref(AVPacket *dst, AVPacket *src)
>>>> src->size = 0;
>>>> }
>>>>
>>>> +int av_packet_make_writable(AVPacket *pkt)
>>>> +{
>>>> + AVBufferRef *buf = NULL;
>>>> + int ret;
>>>> +
>>>> + if (pkt->buf && av_buffer_is_writable(pkt->buf))
>>>> + return 0;
>>>> +
>>>> + if (!pkt->data)
>>>> + return AVERROR(EINVAL);
>>>> +
>>>> + ret = packet_alloc(&buf, pkt->size);
>>>> + if (ret < 0)
>>>> + return ret;
>>>> + if (pkt->size)
>>>> + memcpy(buf->data, pkt->data, pkt->size);
>>>> +
>>>> + av_buffer_unref(&pkt->buf);
>>>> + pkt->buf = buf;
>>>> + pkt->data = buf->data;
>>>> +
>>>> + return 0;
>>>> +}
>>>> +
>>>> void av_packet_rescale_ts(AVPacket *pkt, AVRational src_tb, AVRational
>>>> dst_tb)
>>>> {
>>>> if (pkt->pts != AV_NOPTS_VALUE)
>>>
>>> Why not just call av_buffer_make_writable()? This code seems fine too,
>>> though.
>>
>> That would require duplicating all or most of these checks every time
>> you need to make sure a packet is writable. pkt->buf may be NULL,
>> pkt->buf may already be writable, pkt->data may be NULL, the like.
>>
>> I figured a helper function like this where you just call one function
>> that is "make this packet writable, whatever the current state is" would
>> come in handy and simplify some parts of the tree. See the two commits i
>> mentioned in my reply to Paul, or the mpeg4_unpack_bframes patch i sent
>> last night.
>
> I'll apply this later today or tomorrow unless someone objects.
Pushed.
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