[FFmpeg-devel] [PATCHv6 4/4] libavcodec: v4l2: add support for v4l2 mem2mem codecs

[Jorge Ramirez]

On 08/27/2017 09:09 PM, Jorge Ramirez wrote:
> On 08/25/2017 05:35 PM, wm4 wrote:
>>> +static int buffer_ops_v4l2buf_to_avframe(AVFrame *frame, V4L2Buffer *avbuf)
>>> +{
>>> +    int i, ret;
>>> +
>>> +    av_frame_unref(frame);
>>> +
>>> +    /* 1. get references to the actual data */
>>> +    for (i = 0; i < avbuf->num_planes; i++) {
>>> +        ret = avbuf->ops.buf_to_bufref(avbuf, i, &frame->buf[i]);
>>> +        if (ret)
>>> +            return ret;
>>> +
>>> +        frame->linesize[i] = avbuf->bytesperline[i];
>>> +        frame->data[i] = frame->buf[i]->data;
>>> +    }
>>> +
>>> +    /* 1.1 fixup special cases */
>>> +    switch (avbuf->context->av_pix_fmt) {
>>> +    case AV_PIX_FMT_NV12:
>>> +        if (avbuf->num_planes > 1)
>>> +            break;
>>> +        frame->linesize[1] = avbuf->bytesperline[0];
>>> +        frame->data[1] = frame->buf[0]->data + avbuf->bytesperline[0] * avbuf->context->format.fmt.pix_mp.height;
>>> +        break;
>>> +    default:
>>> +        break;
>>> +    }
>>> +
>>> +    /* 2. get frame information */
>>> +    frame->key_frame = !!(avbuf->buf.flags & V4L2_BUF_FLAG_KEYFRAME);
>>> +    frame->format = avbuf->context->av_pix_fmt;
>>> +
>>> +    /* these values are updated also during re-init in process_video_event */
>>> +    frame->height = avbuf->context->height;
>>> +    frame->width = avbuf->context->width;
>>> +    frame->pts = get_pts(avbuf);
>>> +
>>> +    /* 3. report errors upstream */
>>> +    if (avbuf->buf.flags & V4L2_BUF_FLAG_ERROR) {
>>> +        av_log(avbuf->context->log_ctx, AV_LOG_ERROR, "%s: driver decode error\n", avbuf->context->name);
>>> +        frame->decode_error_flags |= FF_DECODE_ERROR_INVALID_BITSTREAM;
>>> +    }
>>> +
>>> +    return 0;
>>> +}
>> This function seems to lack setting typically required metadata like
>> colorspace.
>>
>
> ok I will retrieve the colorspace from the v4l2 format structure and 
> set it in the frame.

um, I dont see a 1:1 mapping between the colorspaces reported from v4l2 
and what ffmpeg expects (I am also not a subject matter expert on this :( ).

Could I get some guidance on the translation table below please?
btw in my simple tests - ffplay decoded vp8, vp9, mpeg4, mpeg2, h263, 
h264 and hevc I didnt need this field so I am not sure if I am getting 
it right.

TIA

static inline enum AVColorSpace get_colorspace(V4L2Buffer *buf)
{
     enum v4l2_colorspace cs;

     cs = V4L2_TYPE_IS_MULTIPLANAR(buf->context->type) ?
         buf->context->format.fmt.pix_mp.colorspace :
         buf->context->format.fmt.pix.colorspace;

     /* */
     switch (cs) {
     case V4L2_COLORSPACE_SMPTE170M: return AVCOL_SPC_SMPTE170M;
     case V4L2_COLORSPACE_SMPTE240M: return AVCOL_SPC_SMPTE240M;
     case V4L2_COLORSPACE_470_SYSTEM_BG: return AVCOL_SPC_BT470BG;
     case V4L2_COLORSPACE_BT2020: return AVCOL_SPC_BT2020_CL;
     case V4L2_COLORSPACE_REC709: return AVCOL_SPC_BT709;
     case V4L2_COLORSPACE_ADOBERGB:
     case V4L2_COLORSPACE_SRGB:
     case V4L2_COLORSPACE_DCI_P3:
     case V4L2_COLORSPACE_JPEG:
     case V4L2_COLORSPACE_RAW:
     default:
         return AVCOL_SPC_RGB;
     }
}