Re: [FFmpeg-devel] [PATCH] avcodec: add Radiance HDR image format support

[James Almer <jamrial@gmail.com>]

On 7/6/2022 3:47 PM, Paul B Mahol wrote:
> Added parser.
> The test will be added after this is merged.

[...]

> +static int hdr_parse(AVCodecParserContext *s, AVCodecContext *avctx,
> +                     const uint8_t **poutbuf, int *poutbuf_size,
> +                     const uint8_t *buf, int buf_size)
> +{
> +    HDRParseContext *ipc = s->priv_data;
> +    uint64_t state = ipc->pc.state64;
> +    int next = END_NOT_FOUND, i = 0;
> +
> +    s->pict_type = AV_PICTURE_TYPE_NONE;

pict_type I, and key frame?

[...]

> +static int hdr_encode_frame(AVCodecContext *avctx, AVPacket *pkt,
> +                            const AVFrame *frame, int *got_packet)
> +{
> +    HDREncContext *s = avctx->priv_data;
> +    int64_t packet_size;
> +    uint8_t *buf;
> +    int ret;
> +
> +    packet_size = avctx->width * avctx->height * 4LL + 1024LL;
> +    if ((ret = ff_get_encode_buffer(avctx, pkt, packet_size, 0)) < 0)

Wont using worst case scenario like this result in massive packets? 
av_shrink_packet() only changes the size field, it doesn't realloc the 
buffer to shrink it.

You could allocate a buffer in HDREncContext with 
av_fast_padded_malloc() here, use the bytestream2 API below, then 
allocate the packet with ff_get_encode_buffer() using 
bytestream2_tell_p() as size and do a memcpy at the end.

> +        return ret;
> +
> +    buf = pkt->data;
> +    bytestream_put_str(&buf, "#?RADIANCE\n");
> +    bytestream_put_str(&buf, "SOFTWARE=lavc\n");
> +    ret = snprintf(buf, 32, "PIXASPECT=%f\n", av_q2d(av_inv_q(avctx->sample_aspect_ratio)));
> +    if (ret > 0)
> +        buf += ret;
> +    bytestream_put_str(&buf, "FORMAT=32-bit_rle_rgbe\n\n");
> +    ret = snprintf(buf, 32, "-Y %d +X %d\n", avctx->height, avctx->width);
> +    if (ret > 0)
> +        buf += ret;
> +
> +    for (int y = 0; y < avctx->height; y++) {
> +        const float *red   = (const float *)(frame->data[2] + y * frame->linesize[2]);
> +        const float *green = (const float *)(frame->data[0] + y * frame->linesize[0]);
> +        const float *blue  = (const float *)(frame->data[1] + y * frame->linesize[1]);
> +
> +        if (avctx->width < 8 || avctx->width > 0x7fff) {
> +            for (int x = 0; x < avctx->width; x++) {
> +                float2rgbe(buf, red[x], green[x], blue[x]);
> +                buf += 4;
> +            }
> +        } else {
> +            bytestream_put_byte(&buf, 2);
> +            bytestream_put_byte(&buf, 2);
> +            bytestream_put_byte(&buf, avctx->width >> 8);
> +            bytestream_put_byte(&buf, avctx->width & 0xFF);
> +
> +            for (int x = 0; x < avctx->width; x++)
> +                float2rgbe(s->scanline + 4 * x, red[x], green[x], blue[x]);
> +            for (int p = 0; p < 4; p++)
> +                rle(&buf, s->scanline + p, avctx->width);
> +        }
> +    }
> +
> +    pkt->flags |= AV_PKT_FLAG_KEY;
> +
> +    av_shrink_packet(pkt, buf - pkt->data);
> +
> +    *got_packet = 1;
> +
> +    return 0;
> +}

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