> On Aug 7, 2024, at 18:18, Andreas Rheinhardt <andreas.rheinha...@outlook.com>
> wrote:
>
> Zhao Zhili:
>> From: Zhao Zhili <zhiliz...@tencent.com>
>>
>> Before the patch, the method to generate DTS only works with
>> timebase equal to 1/fps. With timebase like 1/1000
>>
>> ./ffmpeg -i foo.mp4 -an -c:v h264_nvenc -enc_time_base 1/1000 bar.mp4
>>
>> pts 0 dts -3
>> pts 160 dts 37
>> pts 80 dts 77
>> pts 40 dts 117 <-- invalid
>> pts 120 dts 157
>> pts 320 dts 197
>> pts 240 dts 237
>> pts 200 dts 277 <-- invalid
>> pts 280 dts 317 <-- invalid
>>
>> The generated DTS can be larger than PTS, since it only reorder the
>> input PTS and minus the number of frame delay, which doesn't take
>> timebase into account. It should minus the "time" of frame delay.
>>
>> 9a245bd trying to fix the issue, but the implementation is incomplete,
>> which only use time_base.num. Then it got reverted by ac7c265b33b.
>>
>> After this patch:
>>
>> pts 0 dts -120
>> pts 160 dts -80
>> pts 80 dts -40
>> pts 40 dts 0
>> pts 120 dts 40
>> pts 320 dts 80
>> pts 240 dts 120
>> pts 200 dts 160
>> pts 280 dts 200
>
> It looks like you only have two reorder frames here, so shouldn't the
> first dts be -80?
But NVENC doesn’t provide the reorder delay value. I have added a comment
without
changing the method to guess a maximum reorder delay. Maybe we can do better by
parse the maximum reorder delay from VPS/SPS/PPS, it’s not the patch supposed
to do. I do hope Nvidia to fix their SDK issues than workaround in FFmpeg.
>> +
>> + // This can be more than necessary, but we don't know the real reorder
>> delay.
>> + delay = FFMAX(ctx->encode_config.frameIntervalP - 1, 0);
>
>> ---
>> libavcodec/nvenc.c | 62 ++++++++++++++++++++++++++++++++++++++--------
>> libavcodec/nvenc.h | 3 +++
>> 2 files changed, 55 insertions(+), 10 deletions(-)
>>
>> diff --git a/libavcodec/nvenc.c b/libavcodec/nvenc.c
>> index ab92395ed6..34448462f0 100644
>> --- a/libavcodec/nvenc.c
>> +++ b/libavcodec/nvenc.c
>> @@ -1893,7 +1893,8 @@ static av_cold int nvenc_setup_surfaces(AVCodecContext
>> *avctx)
>> if (!ctx->frame_data_array)
>> return AVERROR(ENOMEM);
>>
>> - ctx->timestamp_list = av_fifo_alloc2(ctx->nb_surfaces, sizeof(int64_t),
>> 0);
>> + ctx->timestamp_list = av_fifo_alloc2(ctx->nb_surfaces +
>> ctx->encode_config.frameIntervalP,
>> + sizeof(int64_t), 0);
>> if (!ctx->timestamp_list)
>> return AVERROR(ENOMEM);
>>
>> @@ -2347,26 +2348,65 @@ static inline int64_t timestamp_queue_dequeue(AVFifo
>> *queue)
>> return timestamp;
>> }
>>
>> +static inline int64_t timestamp_queue_peek(AVFifo *queue, size_t index)
>> +{
>> + int64_t timestamp = AV_NOPTS_VALUE;
>> + av_fifo_peek(queue, ×tamp, 1, index);
>> +
>> + return timestamp;
>> +}
>> +
>> static int nvenc_set_timestamp(AVCodecContext *avctx,
>> NV_ENC_LOCK_BITSTREAM *params,
>> AVPacket *pkt)
>> {
>> NvencContext *ctx = avctx->priv_data;
>> + int delay;
>> + int64_t delay_time;
>>
>> pkt->pts = params->outputTimeStamp;
>>
>> - if (avctx->codec_descriptor->props & AV_CODEC_PROP_REORDER) {
>> -FF_DISABLE_DEPRECATION_WARNINGS
>> - pkt->dts = timestamp_queue_dequeue(ctx->timestamp_list) -
>> -#if FF_API_TICKS_PER_FRAME
>> - FFMAX(avctx->ticks_per_frame, 1) *
>> -#endif
>> - FFMAX(ctx->encode_config.frameIntervalP - 1, 0);
>> -FF_ENABLE_DEPRECATION_WARNINGS
>> - } else {
>> + if (!(avctx->codec_descriptor->props & AV_CODEC_PROP_REORDER)) {
>> pkt->dts = pkt->pts;
>> + return 0;
>> + }
>> +
>> + // This can be more than necessary, but we don't know the real reorder
>> delay.
>> + delay = FFMAX(ctx->encode_config.frameIntervalP - 1, 0);
>> + if (ctx->output_frame_num >= delay) {
>> + pkt->dts = timestamp_queue_dequeue(ctx->timestamp_list);
>> + ctx->output_frame_num++;
>> + return 0;
>> }
>>
>> + delay_time = ctx->initial_delay_time;
>> + if (!delay_time) {
>> + int64_t t1, t2, t3;
>> + t1 = timestamp_queue_peek(ctx->timestamp_list, delay);
>> + t2 = timestamp_queue_peek(ctx->timestamp_list, 0);
>> + t3 = (delay > 1) ? timestamp_queue_peek(ctx->timestamp_list, 1) :
>> t1;
>> +
>> + if (t1 != AV_NOPTS_VALUE) {
>> + delay_time = t1 - t2;
>> + } else if (avctx->framerate.num > 0 && avctx->framerate.den > 0) {
>> + delay_time = av_rescale_q(delay, (AVRational)
>> {avctx->framerate.den, avctx->framerate.num},
>> + avctx->time_base);
>> + } else if (t3 != AV_NOPTS_VALUE) {
>> + delay_time = delay * (t3 - t2);
>> + } else {
>> + delay_time = delay;
>> + }
>> + ctx->initial_delay_time = delay_time;
>> + }
>> +
>> + /* The following method is simple, but doesn't guarantee monotonic with
>> VFR
>> + * when delay_time isn't accurate (that is, t1 == AV_NOPTS_VALUE)
>> + *
>> + * dts = timestamp_queue_peek(ctx->timestamp_list,
>> ctx->output_frame_num) - delay_time
>> + */
>> + pkt->dts = timestamp_queue_peek(ctx->timestamp_list, 0) - delay_time *
>> (delay - ctx->output_frame_num) / delay;
>> + ctx->output_frame_num++;
>> +
>> return 0;
>> }
>>
>> @@ -2902,4 +2942,6 @@ av_cold void ff_nvenc_encode_flush(AVCodecContext
>> *avctx)
>>
>> nvenc_send_frame(avctx, NULL);
>> av_fifo_reset2(ctx->timestamp_list);
>> + ctx->output_frame_num = 0;
>> + ctx->initial_delay_time = 0;
>> }
>> diff --git a/libavcodec/nvenc.h b/libavcodec/nvenc.h
>> index 09de00badc..dc7fe41951 100644
>> --- a/libavcodec/nvenc.h
>> +++ b/libavcodec/nvenc.h
>> @@ -206,6 +206,9 @@ typedef struct NvencContext
>> AVFifo *output_surface_queue;
>> AVFifo *output_surface_ready_queue;
>> AVFifo *timestamp_list;
>> + // This is for DTS calculating, reset after flush
>> + int64_t output_frame_num;
>> + int64_t initial_delay_time;
>>
>> NV_ENC_SEI_PAYLOAD *sei_data;
>> int sei_data_size;
>
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