[FFmpeg-devel] [PATCH v2] lavf/avienc: Use palette side data packet if available

[Mats Peterson]

On 02/28/2016 01:13 AM, Mats Peterson wrote:
> On 02/28/2016 12:34 AM, Reimar Döffinger wrote:
>
>> On Sat, Feb 27, 2016 at 10:55:13PM +0100, Mats Peterson wrote:
>>> -                if (!avist->hdr_pal_done) {
>>> -                    int64_t cur_offset = avio_tell(pb);
>>> -                    avio_seek(pb, avist->pal_offset, SEEK_SET);
>>> -                    for (i = 0; i < pal_size; i++) {
>>> -                        uint32_t v = AV_RL32(data + size -
>>> 4*pal_size + 4*i);
>>> -                        avio_wl32(pb, v & 0xffffff);
>>> -                    }
>>> -                    avio_seek(pb, cur_offset, SEEK_SET);
>>> -                    avist->hdr_pal_done++;
>>> -                }
>>
>> Hadn't seen this before.
>> In principle it is a bit unfortunate as it means that streaming via
>> stdout is not possible.
>> It should at least be suppressed when seeking the output stream
>> is not possible.
>
> Right. Good point.
>
>>
>>
>>> +        for (i = 0; i < pkt->side_data_elems; i++) {
>>> +            if (pkt->side_data[i].type == AV_PKT_DATA_PALETTE) {
>>> +                pal = pkt->side_data[i].data;
>>> +                break;
>>> +            }
>>> +        }
>>
>> av_frame_get_side_data
>
> No frames available in a muxer (as far as I know). But thanks anyway...
>
>>
>>> -                    uint32_t v = AV_RL32(data + size - 4*pal_size +
>>> 4*i);
>>> -                    avio_wb32(pb, v<<8);
>>> +                    uint32_t v = AV_RL32(pal + 4*i);
>>> +                    avio_wl32(pb, v & 0xffffff);
>>
>> You'll probably still need the if to use the one or the avio_w...
>> depending on format.
>> Unless it's possible to change the embedded format to match
>> the side data one.
>>
>
> Don't know what you mean by "Probably still need the if".
>
>
>>> +            for (i = 0; i < pal_size; i++) {
>>> +                uint32_t v = AV_RL32(pal + 4*i);
>>> +                avio_wb32(pb, v<<8);
>>
>> Why is the header format different? That seems a bit weird.
>> _______________________________________________
>
> The palette uses a RGBQUAD (BGRA) structure for the entries in the
> palette after the BITMAPINFOHEADER, but it uses an AVIPALCHANGE
> structure (RGBA) for those 'xxpc' chunks. It may seem a bit confusing,

Well, the AVIPALCHANGE structure uses a PALETTEENTRY structure, that's 
the core of it, and it uses RGB order, with a flag byte afterwards.