On Mon, 28 Aug 2017 10:21:54 +0200
Jorge Ramirez <jorge.ramirez-or...@linaro.org> wrote:
> On 08/25/2017 05:35 PM, wm4 wrote:
> >> +int avpriv_v4l2m2m_reinit(V4L2Context* ctx)
> >> +{
> >> + V4L2m2mContext *s = container_of(ctx, V4L2m2mContext, capture);
> >> + int ret;
> >> +
> >> + av_log(ctx->log_ctx, AV_LOG_DEBUG, "%s reinit context\n", ctx->name);
> >> +
> >> + /* 1. streamoff */
> >> + ret = avpriv_v4l2_context_set_status(ctx, VIDIOC_STREAMOFF);
> >> + if (ret)
> >> + av_log(ctx->log_ctx, AV_LOG_ERROR, "VIDIOC_STREAMOFF %s\n",
> >> ctx->name);
> >> +
> >> + /* 2. unmap the buffers (v4l2 and ffmpeg) */
> >> + avpriv_v4l2_context_release(ctx);
> > What happens to AVFrames or AVPackets that are still referenced?
> >
>
> yes in response to your previous comment on the subject, I am trying to
> address that in v7 not releasing the context while there are buffers on
> the fly....
> This is what I came up with (if you can suggest something better - ie, a
> way to block until the AVBufferRefs are unref- please let me know)
>
> void avpriv_v4l2_context_release(V4L2Context* ctx)
> {
> int i, ret;
>
> if (!ctx->buffers)
> return;
>
> /* wait until all buffers are no longer in use */
> for (i = 0; i < ctx->num_buffers; i++) {
>
> if (ctx->buffers[i].status & (V4L2BUF_IN_DRIVER |
> V4L2BUF_AVAILABLE))
> continue;
>
> while (ctx->buffers[i].status & V4L2BUF_RET_USER)
> usleep(100);
> }
>
> ret = ctx->ops.release_buffers(ctx);
> if (ret)
> av_log(ctx->log_ctx, AV_LOG_WARNING, "V4L2 failed to unmap the
> %s buffers\n", ctx->name);
> else
> av_log(ctx->log_ctx, AV_LOG_DEBUG, "%s buffers unmapped\n",
> ctx->name);
>
> av_free(ctx->buffers);
> ctx->buffers = NULL;
> ctx->num_queued = 0;
> }
>
No, this is not possible. You must make the V4L state reference
counted, and AVBufferRefs must implicitly reference this context.
AVHWFramesContext does this in a more elegant way - it's a frame pool
specifically made for hw decoders. I suspect the V4L code should be
ported to that. I hope Mark Thompson has some helpful remarks on this.
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