Apr 11, 2020, 15:56 by s...@jkqxz.net:
> On 04/04/2020 21:26, Andriy Gelman wrote:
>
>> From: Andriy Gelman <andriy.gel...@gmail.com>
>>
>> The dequeued packets from vp8 (s5p-mfc) encoder are output in ivf format
>> which breaks the stream when the packets are muxed in avformat. This commit
>> adds an option to remove the container and thus support the encoder.
>>
>> Signed-off-by: Andriy Gelman <andriy.gel...@gmail.com>
>> ---
>> libavcodec/v4l2_m2m.h | 2 ++
>> libavcodec/v4l2_m2m_enc.c | 53 +++++++++++++++++++++++++++++++--------
>> 2 files changed, 45 insertions(+), 10 deletions(-)
>>
>> diff --git a/libavcodec/v4l2_m2m.h b/libavcodec/v4l2_m2m.h
>> index 456281f48c..525f9456e9 100644
>> --- a/libavcodec/v4l2_m2m.h
>> +++ b/libavcodec/v4l2_m2m.h
>> @@ -73,6 +73,8 @@ typedef struct V4L2m2mPriv {
>>
>> int num_output_buffers;
>> int num_capture_buffers;
>> + int strip_ivf;
>> + int ivf_detected;
>> } V4L2m2mPriv;
>>
>> /**
>> diff --git a/libavcodec/v4l2_m2m_enc.c b/libavcodec/v4l2_m2m_enc.c
>> index c9f1741bfd..9c11f90567 100644
>> --- a/libavcodec/v4l2_m2m_enc.c
>> +++ b/libavcodec/v4l2_m2m_enc.c
>> @@ -25,6 +25,8 @@
>> #include <sys/ioctl.h>
>> #include <search.h>
>> #include "libavcodec/avcodec.h"
>> +#include "libavcodec/internal.h"
>> +#include "libavutil/intreadwrite.h"
>> #include "libavutil/pixdesc.h"
>> #include "libavutil/pixfmt.h"
>> #include "libavutil/opt.h"
>> @@ -256,6 +258,7 @@ static int v4l2_send_frame(AVCodecContext *avctx, const
>> AVFrame *frame)
>>
>> static int v4l2_receive_packet(AVCodecContext *avctx, AVPacket *avpkt)
>> {
>> + V4L2m2mPriv *priv = avctx->priv_data;
>> V4L2m2mContext *s = ((V4L2m2mPriv*)avctx->priv_data)->context;
>> V4L2Context *const capture = &s->capture;
>> V4L2Context *const output = &s->output;
>> @@ -281,7 +284,28 @@ static int v4l2_receive_packet(AVCodecContext *avctx,
>> AVPacket *avpkt)
>> }
>>
>> dequeue:
>> - return ff_v4l2_context_dequeue_packet(capture, avpkt);
>> + ret = ff_v4l2_context_dequeue_packet(capture, avpkt);
>> + if (ret)
>> + return ret;
>> +
>> + if (priv->strip_ivf) {
>> + int header_offset = 0;
>> + if (avpkt->size >= 32 && AV_RL32(avpkt->data) ==
>> MKTAG('D','K','I','F')) {
>> + header_offset = 32;
>> + priv->ivf_detected = 1;
>> + } else if (priv->ivf_detected) {
>> + header_offset = 12;
>> + }
>> + header_offset = FFMIN(header_offset, avpkt->size);
>> + avpkt->data += header_offset;
>> + avpkt->size -= header_offset;
>> +
>> + if (avpkt->size == 0) {
>>
>
> Does this case ever happen? Wouldn't something have gone very wrong here to
> get here?
>
>> + av_packet_unref(avpkt);
>> + goto dequeue;
>> + }
>> + }
>> + return 0;
>> }
>>
>
> Could the presence of the IVF container be autodetected? I suspect it can,
> because the tag will collide with the fixed start code in the intra frame at
> the start of the stream. If that were possible then it would avoid having
> the tricky option which users are not going to easily know about.
>
> Otherwise seems ok. It's rather horrible, but it looks like the best
> solution to the problem.
>
I really, really don't think its a good idea to probe the packets of encoders,
so I think I'm NAK on this patch for now.
If a spec-compliant encoder cannot produce a packet that starts with DKIF, I'd
be okay with it though.
Or if ivf had a CRC at the end like ogg where a match would practically
guarantee its an ivf packet. Otherwise, its just too fragile.
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